# Jaskamal Kainth: full text

> Chief Software Engineer at Samsung R&D Institute India, leading engineering for Samsung's global product search platform (query understanding, retrieval, ranking). B.E. Computer Science and M.Sc. Mathematics from BITS Pilani; ACM-ICPC competitor and long-time competitive programmer.

Every article on https://jaskamalkainth.github.io, as Markdown. Each section starts with the article's canonical URL;
please cite that URL when quoting. Index of articles: https://jaskamalkainth.github.io/llms.txt


---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotes.html
Title: C++ Notes: Templates, Lambdas, constexpr and the STL
Description: Short, example-first notes on modern C++: template specialization and metaprogramming, overloading, lambdas, constexpr, variadic templates, tuples and unordered_map.
Published: 2021-05-07
Updated: 2026-10-02

<div class="pl-hero">
  <div>
    <h1>C++ Notes</h1>
    <p class="pl-lede">Short, example-first notes on the corners of C++ I keep coming back to: templates, compile-time computation and the standard library.</p>
  </div>
  <img src="/img/cpplogo.png" alt="C++ logo" width="220" height="164" loading="lazy">
</div>

<ol class="note-list">
</ol>

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/1.html
Title: Template explicit vs implicit specialization
Description: Why a C++ explicit specialization declared as f(const int) still matches f(int): top-level const is not part of the function type. Worked example.
Published: 2023-03-24
Updated: 2026-10-02

# Template explicit vs implicit specialization

**Short answer:** top-level `const` on a by-value parameter is not part of a function's type, so `template<> void f(const int)` is the explicit specialization of `f<int>`. Calling `f` with an `int` (const or not) runs the specialization. Any other argument type falls back to an implicit instantiation of the primary template.

```c++
    #include <iostream>
    using std::cout;

    // Main template
    template<class T>
    void f(T n) {
        cout << 2;
    }
    // Template specialization
    template<>
    void f(const int n) {
        cout << 1;
    }

    int main() {
        int n = 11;
        f(n);
    }
```
``` Code outputs 1. ```

 For the function call f(n), since 'n' is of int type, the template argument T is deduced as T = int.

 The explicit specialization
 ```c++
 template<> void f(const int n)
 ```
 looks like it is for `const int`, but when a function type is formed the top-level `const` on a by-value parameter is dropped. Its signature is `void(int)`, so it is the specialization for T = int and it is the one that runs.

 The `const` still matters inside the body: `n` cannot be modified there. It just doesn't change which calls match.

 Passing a `const int` also outputs 1, because template argument deduction drops top-level `const` from a by-value argument too (T = int).

 To see the primary template, call `f` with a different type: `f(2.0)` deduces T = double, no specialization exists for it, so the compiler implicitly instantiates `f<double>` and the code outputs 2.

> Explicit specializations do not take part in overload resolution. The compiler first picks the best primary template for the call (deducing T), and only then checks whether an explicit specialization exists for those exact template arguments. If one does, it is used; otherwise the primary template is implicitly instantiated.


*********************************************************************

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/10.html
Title: std::unordered_map in C++
Description: std::unordered_map in C++: a hash table with average O(1) lookup, insert and erase, basic usage, and custom hash functions for user-defined keys.
Published: 2023-04-06
Updated: 2026-10-02

# Unordered Map in C++

`std::unordered_map` is a container that stores key-value pairs in which keys are unique. It implements a hash table, providing average constant-time complexity for search, insert, and delete operations.

## Basic Usage

```cpp
#include <unordered_map>
#include <string>
#include <iostream>

int main() {
    // Create an unordered_map
    std::unordered_map<std::string, int> ages;
    
    // Insert elements
    ages["Alice"] = 30;
    ages["Bob"] = 25;
    ages.insert({"Charlie", 35});
    
    // Access elements
    std::cout << "Alice's age: " << ages["Alice"] << std::endl;
    
    // Check if key exists
    if (ages.find("David") == ages.end()) {
        std::cout << "David not found" << std::endl;
    }
    
    // Iterate through all elements (structured bindings need C++17)
    for (const auto& [name, age] : ages) {
        std::cout << name << " is " << age << " years old" << std::endl;
    }
    
    return 0;
}
```

## Custom Hash Functions

For custom types as keys, you need to provide a hash function and equality operator:

```cpp
struct Person {
    std::string name;
    int age;
    
    bool operator==(const Person& other) const {
        return name == other.name && age == other.age;
    }
};

// Custom hash function. XOR is the simplest way to combine hashes but collides easily
// (equal component hashes cancel out to 0); boost::hash_combine-style mixing is safer.
struct PersonHash {
    std::size_t operator()(const Person& p) const {
        return std::hash<std::string>()(p.name) ^ std::hash<int>()(p.age);
    }
};

// Usage
std::unordered_map<Person, std::string, PersonHash> personData;
```

`std::unordered_map` is generally preferred over `std::map` when order doesn't matter and you need faster lookups for large datasets.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/2.html
Title: Ambiguous function overloading in C++: why foo(0) is ill-formed
Description: Why calling foo(0) fails to compile when foo(const char*) and foo(short) both exist: 0 converts to either with equal rank, so the call is ambiguous.
Published: 2023-03-24
Updated: 2026-10-02

# Ill-formed function call due to ambiguous function overloading

**Short answer:** `foo(0)` is ambiguous because the literal `0` is both an `int` and a null pointer constant. Converting it to `const char*` (pointer conversion) and to `short` (integral conversion) are both standard conversions of the same rank, so neither overload is better and the call does not compile.

```c++
#include <iostream>

void foo(const char* str) // Function 1
{
    std::cout << "F1 = " << str << std::endl;
}
void foo(short n) // Function 2
{
    std::cout << "F2 = " << n << std::endl;
}
int main()
{
    foo("randomString"); // Function 1 is called
    foo(1); // Function 2 is called

    foo(0); 
    // In this case 0 can be implicitly treated as a null pointer or an integer
    // so with 1 implicit conversion sequence compiler can deduce either of the Function 1 or 2
    // Hence it is an ill-formed function call and a compilation error.
    return 0;
}
```
**Compilation Error:**
```     
    ill-formed-function-call.cpp:16:5: error: call to 'foo' is ambiguous
        foo(0); 
        ^~~
    ill-formed-function-call.cpp:3:6: note: candidate function
    void foo(const char* str) // Function 1
        ^
    ill-formed-function-call.cpp:7:6: note: candidate function
    void foo(short n) // Function 2
        ^
    1 error generated.
```
* In the above code, both foo() overloads are viable and for a compiler to choose, one of them has to have a better conversion sequence but since 0 is of type int and also a nullptr constant, in both cases we have a single conversion and hence no function is better than the other hence ill-formed.
* If the function definition had foo(int) then the compiler can treat 0 as integer without any implicit conversion and hence no error.
* Similarly if we pass foo(0L) and we have a definition like foo(long n).
> Note: a *null pointer constant* is an integer literal with value 0 (or `nullptr`). Passing `nullptr` instead of `0` would unambiguously call Function 1.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/3.html
Title: Template metaprogramming in C++: compile-time Fibonacci
Description: Compute Fibonacci numbers at compile time with C++ template metaprogramming: a recursive struct template with explicit specializations as base cases.
Published: 2023-04-06
Updated: 2026-10-02

# Template Metaprogramming - Fibonacci

Template metaprogramming is a technique in C++ that uses templates to perform computations at compile time.

## Fibonacci Implementation

The Fibonacci sequence can be implemented using template metaprogramming:

```cpp
template<int N>
struct Fibonacci {
    static const int value = Fibonacci<N-1>::value + Fibonacci<N-2>::value;
};

// Base cases
template<>
struct Fibonacci<0> {
    static const int value = 0;
};

template<>
struct Fibonacci<1> {
    static const int value = 1;
};
```

This implementation computes Fibonacci numbers at compile time, making runtime computation unnecessary. The template specializations for `N=0` and `N=1` serve as base cases to terminate the recursion.

Using this implementation, `Fibonacci<10>::value` would give you the 10th Fibonacci number, all calculated during compilation.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/4.html
Title: Template metaprogramming in C++: compile-time factorial
Description: Compute factorials at compile time in C++ with a recursive class template and a Factorial<0> base case, so the result has no runtime cost.
Published: 2023-04-06
Updated: 2026-10-02

# Template Metaprogramming - Factorial

Another classic example of template metaprogramming is computing factorials at compile time.

## Factorial Implementation

```cpp
template<int N>
struct Factorial {
    static const int value = N * Factorial<N-1>::value;
};

// Base case
template<>
struct Factorial<0> {
    static const int value = 1;
};
```

This implementation allows factorial computations to be performed during compilation. The template is recursively instantiated until it reaches the base case of `Factorial<0>`, which returns 1.

To use this implementation, simply access the `value` member of the appropriate template instantiation:

```cpp
int main() {
    std::cout << "Factorial of 5: " << Factorial<5>::value << std::endl; // 120
    return 0;
}
```

The computation happens at compile time, resulting in no runtime overhead for the calculation.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/5.html
Title: Lambda expressions in C++
Description: C++ lambda expressions explained: syntax, capture lists, capturing by value, mutable lambdas, and using lambdas with standard algorithms.
Published: 2023-04-06
Updated: 2026-10-02

# Lambda Expressions in C++

Lambda expressions were introduced in C++11 and provide a concise way to create anonymous function objects.

## Basic Syntax

The basic syntax of a lambda expression is:

```cpp
[capture-list](parameter-list) -> return-type { function-body }
```

Where:
- `capture-list`: Specifies which variables from the surrounding scope are accessible
- `parameter-list`: Similar to function parameters
- `return-type`: Optional, compiler can often deduce it
- `function-body`: The code to execute

## Examples

### Simple Lambda

```cpp
auto add = [](int a, int b) { return a + b; };
std::cout << add(5, 3); // Outputs: 8
```

### Capturing Variables

```cpp
int multiplier = 5;
auto multiply = [multiplier](int x) { return x * multiplier; };
std::cout << multiply(3); // Outputs: 15
```

### Mutable Lambda

By default, variables captured by value cannot be modified. Use the `mutable` keyword to allow modification:

```cpp
int counter = 0;
auto increment = [counter]() mutable { return ++counter; };
std::cout << increment(); // Outputs: 1
std::cout << counter;     // Outputs: 0 (original not modified)
```

Lambda expressions are commonly used with algorithms from the standard library, such as `std::sort`, `std::for_each`, and `std::transform`.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/6.html
Title: constexpr in C++
Description: How constexpr moves work to compile time in C++11/14/17: constexpr functions, compile-time vs runtime evaluation, and why it beats template metaprogramming.
Published: 2023-04-06
Updated: 2026-10-02

# Constexpr in C++

The `constexpr` keyword was introduced in C++11 and enhanced in C++14 and C++17. It enables computations to be performed at compile time.

## Basic Usage

A `constexpr` function can be evaluated at compile time if its arguments are compile-time constants:

```cpp
constexpr int square(int x) {
    return x * x;
}

// Used at compile time
constexpr int result = square(5); // Computed during compilation

// Used at runtime
int input;
std::cin >> input;
int dynamic_result = square(input); // Computed at runtime
```

## Constexpr vs Template Metaprogramming

While template metaprogramming also enables compile-time computation, `constexpr` provides a more readable and maintainable approach:

```cpp
// Fibonacci with constexpr (C++14 and later)
constexpr int fibonacci(int n) {
    if (n <= 1) return n;
    return fibonacci(n-1) + fibonacci(n-2);
}

// Usage
constexpr int fib10 = fibonacci(10); // Computed at compile time
```

The advantage of `constexpr` over template metaprogramming is that it uses familiar function syntax rather than recursive template instantiations, making the code easier to understand and maintain.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/7.html
Title: Struct vs class in C++
Description: The only differences between struct and class in C++ are default member access and default inheritance (public vs private). When to use each.
Published: 2023-04-06
Updated: 2026-10-02

# Struct vs Class in C++

In C++, `struct` and `class` are nearly identical, with only one difference in their default access level.

## Key Differences

| Feature | Struct | Class |
|---------|--------|-------|
| Default access modifier | public | private |
| Default inheritance | public | private |
| Intended use (convention) | Passive data structures | Objects with behavior |

## Example

```cpp
struct Point {
    int x; // public by default
    int y; // public by default
};

class Circle {
private: // private by default, but explicitly shown for clarity
    Point center;
    double radius;
    
public:
    Circle(Point c, double r) : center(c), radius(r) {}
    double area() const { return 3.14159 * radius * radius; }
};
```

## When to Use Each

- Use `struct` when you have a simple data structure with little or no behavior
- Use `class` when you have an object with both data and behavior that operates on that data
- Use `struct` when all members should be publicly accessible
- Use `class` when you need to enforce encapsulation by making some members private

The choice between `struct` and `class` is often a matter of convention and communicating intent to other programmers.

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/8.html
Title: Variadic templates in C++
Description: Variadic templates in C++11: parameter packs, recursive expansion with a base case, C++17 fold expressions, and where they are used.
Published: 2023-04-06
Updated: 2026-10-02

# Variadic Templates in C++

Variadic templates, introduced in C++11, allow you to define templates that accept an arbitrary number of arguments of any type.

## Basic Syntax

```cpp
template<typename... Args>
return_type function_name(Args... args);
```

The ellipsis (`...`) indicates a parameter pack, which can contain zero or more template arguments.

## Recursive Implementation Example

A common pattern is to use recursion to process variadic templates:

```cpp
// Base case to terminate recursion
void print() {
    std::cout << std::endl;
}

// Recursive case
template<typename T, typename... Args>
void print(T first, Args... rest) {
    std::cout << first << " ";
    print(rest...); // Recursive call with remaining arguments
}

// Usage
print(1, 2.5, "hello", 'c'); // Outputs: 1 2.5 hello c
```

## Fold Expressions (C++17)

C++17 introduced fold expressions to simplify variadic template code:

```cpp
template<typename... Args>
auto sum(Args... args) {
    return (... + args); // Unary left fold
}

// Usage
int total = sum(1, 2, 3, 4, 5); // 15
```

## Applications

Variadic templates are particularly useful for:
- Creating type-safe variadic functions
- Implementing perfect forwarding
- Building tuple-like data structures
- Creating compile-time type lists

---

URL: https://jaskamalkainth.github.io/blog_posts/CppNotesDb/9.html
Title: std::tuple in C++
Description: Using std::tuple in C++: creating tuples, std::get, std::make_tuple, C++17 structured bindings and class template argument deduction, and std::tuple_cat.
Published: 2023-04-06
Updated: 2026-10-02

# Tuples in C++

`std::tuple` is a template class in C++ that can hold a fixed-size collection of elements of different types.

## Basic Usage

```cpp
#include <tuple>
#include <iostream>
#include <string>

int main() {
    // Creating a tuple
    std::tuple<int, std::string, double> person(30, "John", 6.1);
    
    // Accessing elements using std::get
    std::cout << "Age: " << std::get<0>(person) << std::endl;
    std::cout << "Name: " << std::get<1>(person) << std::endl;
    std::cout << "Height: " << std::get<2>(person) << std::endl;
    
    // C++17 structured binding
    auto [age, name, height] = person;
    std::cout << "Name: " << name << std::endl;
    
    return 0;
}
```

## Tuple Operations

### Creating Tuples

```cpp
// Using make_tuple helper
auto person = std::make_tuple(30, "John", 6.1);

// C++17 class template argument deduction
std::tuple person2(30, "John", 6.1);
```

### Tuple Concatenation

```cpp
// C++11 and later
auto tuple1 = std::make_tuple(1, 'a');
auto tuple2 = std::make_tuple("hello", 5.5);
auto combined = std::tuple_cat(tuple1, tuple2); // tuple<int, char, const char*, double>
```

Tuples are especially useful when you need to return multiple values from a function or when you need to group heterogeneous data without defining a custom class.

---

URL: https://jaskamalkainth.github.io/blog_posts/DSU_problems.html
Title: Disjoint Set Union (Union-Find) Practice Problems
Description: Practice problems for Disjoint Set Union (union–find) from UVa, HackerEarth and Codeforces, ordered by difficulty: connected components, group leaders and merges.
Published: 2016-05-07
Updated: 2026-10-02

<div class="pl-hero">
  <div>
    <h1>Disjoint Set Union Problems</h1>
    <p class="pl-lede">Union–find answers "are these two in the same group?" in near-constant time. These problems start with counting components and build up to tracking leaders and merging whole ranges. Tick off the ones you solve; your progress is saved in this browser.</p>
  </div>
  <img src="/img/dsu.jpg" alt="Two disjoint-set trees being merged by attaching one root under the other" width="220" height="150" loading="lazy">
</div>

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## Frequently asked questions

### What is a disjoint set union (union–find) data structure?

Disjoint set union keeps a collection of non-overlapping sets as a forest, where each tree's root is the set's representative. find(x) returns x's root and union(a, b) links two roots, so you can merge groups and ask whether two elements are in the same group.

### What is the time complexity of union–find?

With both path compression and union by rank (or size), any sequence of m operations on n elements runs in O(m · α(n)) time, where α is the inverse Ackermann function. α(n) is at most 4 for any practical n, so each operation is effectively constant time.

### When should I use DSU instead of BFS or DFS?

Use DSU when edges arrive over time and you repeatedly ask whether two nodes are connected, or when you need to merge groups (for example in Kruskal's minimum spanning tree). BFS/DFS is simpler when the graph is fixed and you only need to explore it once.


---

URL: https://jaskamalkainth.github.io/blog_posts/best-samsung-phones-under-50000.html
Title: Best Samsung Phones Under ₹50,000 in India (2026 Guide)
Description: The best Samsung phones under ₹50,000 in India for 2026: Galaxy A36 5G for display, M47 5G for battery, M17e 5G on a budget, with prices and key specs.
Published: 2026-01-15
Updated: 2026-01-15

# Best Samsung Phones Under ₹50,000 (2026)

> **Quick answer:** buy the **Galaxy A36 5G** (from ₹33,999) for the best screen, the **Galaxy M47 5G** (₹28,999) for the biggest battery, or the **Galaxy M17e 5G** (₹12,499) if you want to spend as little as possible. Prices are Samsung India's listed prices as of January 2026.

*Disclosure: I work at Samsung R&D Institute India. This is a personal post, not an official Samsung publication; it is based only on Samsung India's public product pages, linked throughout.*

Samsung's ₹50,000-and-under lineup spans the Galaxy M and Galaxy A series — from ultra-budget picks under ₹15,000 to near-flagship Super AMOLED displays just under the ₹35,000 mark. Here's how the current lineup breaks down, pulled directly from [Samsung India's "Best Mobiles under ₹50,000" page](https://www.samsung.com/in/smartphones/mobiles-by-price/under-rs50000/) and each model's own buy page.

## Quick Picks

| Phone | Starting Price | Best For |
|---|---|---|
| [Galaxy A36 5G](https://www.samsung.com/in/smartphones/galaxy-a36/buy/) | ₹33,999 | Best overall (Super AMOLED, 120Hz) |
| [Galaxy M47 5G](https://www.samsung.com/in/smartphones/galaxy-m/galaxy-m47-5g-rogue-red-128gb-sm-m476bzrdins/buy/) | ₹28,999 | Best battery life (6000mAh) |
| [Galaxy M17e 5G](https://www.samsung.com/in/smartphones/galaxy-m/galaxy-m17e-5g-blitz-blue-128gb-sm-m076blbains/buy/) | ₹12,499 | Best budget pick |

## 1. Galaxy A36 5G — Best Overall

- **Display:** 6.7" Super AMOLED, 120Hz refresh rate
- **RAM / Storage:** 8GB/128GB, 8GB/256GB, or 12GB/256GB
- **Colors:** Awesome Black, Lavender, White, Lime, Sapphire Blue, Emerald Green
- **Price:** Starting ₹33,999 (9-month no-cost EMI from ₹3,778/mo; ₹1,000 off first purchase)

👉 **[See current price & configure →](https://www.samsung.com/in/smartphones/galaxy-a36/buy/)**

The A36 5G is the pick if you want the closest thing to a flagship screen (Super AMOLED + 120Hz) without crossing ₹35,000. Best for anyone who spends a lot of time on video/social media and notices screen quality.

## 2. Galaxy M47 5G — Best Battery Life

- **Battery:** 6000 mAh (typical)
- **Display:** ~6.7" (16.91cm)
- **RAM / Storage:** 8GB with 128GB or 256GB storage
- **Colors:** Blaze Blue, Rogue Red
- **Price:** ₹28,999 launch offer (₹4,000 instant bank discount)

👉 **[See current price & configure →](https://www.samsung.com/in/smartphones/galaxy-m/galaxy-m47-5g-rogue-red-128gb-sm-m476bzrdins/buy/)**

If your phone needs to survive a full day of classes/work without a charger in sight, the M47 5G's 6000mAh battery is the standout spec in this price range.

## 3. Galaxy M17e 5G — Best Budget Pick

- **RAM / Storage:** 128GB (see product page for RAM configuration)
- **Colors:** Blitz Blue and others
- **Price:** ₹12,499

👉 **[See current price & configure →](https://www.samsung.com/in/smartphones/galaxy-m/galaxy-m17e-5g-blitz-blue-128gb-sm-m076blbains/buy/)**

At under ₹13,000, this is less a "best under ₹50,000" pick and more proof of how far your budget stretches in Samsung's current 5G lineup — a solid choice if ₹50,000 is your ceiling, not your target.

*(Full, filterable list: [Samsung India — Best Mobiles under ₹50,000](https://www.samsung.com/in/smartphones/mobiles-by-price/under-rs50000/))*

## How We Chose These

Picks were pulled directly from Samsung India's own "under ₹50,000" category page and each model's individual buy page, prioritizing models Samsung itself currently features as in-stock/buyable (not older or discontinued models still indexed elsewhere on the site) — then split by what most buyers optimize for: screen quality, battery life, and raw budget.

## Conclusion

If you just want one answer: the **Galaxy A36 5G** (from ₹33,999) is the best all-round pick under ₹50,000 — it's the only one of the three with a Super AMOLED 120Hz display, and it still leaves ₹16,000+ of headroom under the budget cap. Pick the **M47 5G** instead if battery life matters more to you than screen quality, or the **M17e 5G** if you'd rather spend a fraction of the budget and put the rest toward accessories, a case, or savings.

*Prices shown are Samsung's listed starting prices at the time of writing and include current launch/bank offers — check each buy page linked above for live pricing before purchasing.*

## Frequently asked questions

### Which is the best Samsung phone under ₹50,000 in 2026?

The Galaxy A36 5G (from ₹33,999) is the best all-round pick: it is the only phone of the three with a 6.7-inch Super AMOLED 120Hz display, and it leaves more than ₹16,000 of headroom under a ₹50,000 budget.

### Which Samsung phone under ₹50,000 has the best battery?

The Galaxy M47 5G, with a 6000mAh (typical) battery, at a ₹28,999 launch offer price.

### What is the cheapest 5G Samsung phone in this list?

The Galaxy M17e 5G at ₹12,499 with 128GB of storage.


---

URL: https://jaskamalkainth.github.io/blog_posts/bloom_filters.html
Title: Bloom Filters Explained: How They Work, False Positives and C++ Code
Description: How a Bloom filter answers set membership with no false negatives and a tunable false-positive rate: the bit array, hash functions, formulas, real uses and C++ code.
Published: 2025-03-15
Updated: 2026-10-02

# Bloom Filters: The Art of Probably Knowing

> **In short:** a Bloom filter is a bit array plus *k* hash functions that tells you whether an element is **definitely not** in a set or **probably** in it. It never gives false negatives, its false-positive rate is tunable (about 1% at ~10 bits per element), and it uses a few bits per element regardless of element size. Databases, browsers and caches use it to skip expensive lookups for things that aren't there.

Imagine you're a bouncer at a club. You have a list of people who are banned. For every person who walks up, you need to decide: are they on the ban list?

The naive approach (scanning the entire list every time) is slow and expensive. But you don't necessarily need *certainty*. You just need a fast answer to: **"Is this person definitely NOT banned?"** If the answer is yes, let them in quickly. If there's any doubt, do the full check.

That's the intuition behind a **Bloom filter**.

## The Core Idea

A Bloom filter is a space-efficient data structure with one peculiar property:

- It can tell you with **100% certainty** that something is **not** in a set.
- It can tell you that something is **probably** in the set, but might occasionally be wrong (a false positive).

It **never** produces false negatives. If you added something, the Bloom filter will always recognize it.

This asymmetry ("definitely no" vs. "probably yes") turns out to be incredibly useful.

## How It Works (Simply)

Picture a row of light switches, all starting in the **OFF** position.

**Adding an element:**
1. Run the element through several different hash functions. Each one gives you a number.
2. Flip the switches at those numbered positions to **ON**.

**Checking if an element exists:**
1. Run the same element through the same hash functions.
2. Look at those switch positions.
3. If **any** switch is **OFF** → the element was definitely never added.
4. If **all** switches are **ON** → the element was *probably* added (but another combination of elements could have flipped those same switches).

That's it. No storing the actual elements, just flipping bits.

<div class="demo-link">
  <a href="/blog_posts/experiments/bloom-filter/index.html" class="btn btn-primary">
    <i class="fa fa-play-circle"></i> Try the Interactive Bloom Filter Demo
  </a>
</div>

## Real-World Use Cases

This might sound abstract, so let's look at where this is actually used in production systems you interact with every day.

### 1. Chrome's Safe Browsing

Every time you visit a URL, Chrome checks whether it's a known phishing or malware site. Google maintains a list of hundreds of millions of dangerous URLs.

Downloading that full list to your browser every time would be impractical. Early versions of Chrome instead kept a **Bloom filter** of dangerous URL prefixes locally (a few MB); it was later replaced by a more compact "prefix set", but the idea is the same. When you navigate to a site:

- If the Bloom filter says **"definitely not in the list"** → proceed immediately, no network call needed.
- If it says **"probably dangerous"** → Chrome makes a real network call to verify before loading the page.

The vast majority of URLs are safe, so the Bloom filter eliminates almost all network checks with zero false negatives.

### 2. Databases Avoiding Unnecessary Disk Reads (Cassandra, HBase, LevelDB)

Disk reads are orders of magnitude slower than memory reads. Databases like Cassandra and LevelDB use Bloom filters to answer: "Does this key exist in this file on disk?"

Before reading from disk, they check the Bloom filter:
- **"Definitely not here"** → skip this file entirely, saving a costly I/O operation.
- **"Probably here"** → do the actual disk read.

In LSM-tree databases a single key can live in any of many on-disk files, so this lets a read skip almost every file that doesn't contain the key. Cassandra exposes the trade-off directly as a per-table `bloom_filter_fp_chance` setting.

### 3. Medium's "Already Read" Articles

Medium used Bloom filters to track which articles a user has already seen, so they don't recommend the same article twice.

Storing every article ID a user has ever viewed in a database per user would be expensive at scale. A Bloom filter per user takes a tiny fraction of that space. A false positive just means occasionally not recommending an article the user hasn't actually read, a minor, acceptable inconvenience.

### 4. Bitcoin Lite Clients (SPV Nodes)

Bitcoin's lightweight clients (that don't download the full blockchain) use Bloom filters to ask full nodes: "Send me only transactions relevant to my wallet addresses."

The client sends a Bloom filter encoding its addresses. The full node filters transactions through it. This avoids revealing which specific addresses the client owns (partial privacy) while dramatically reducing the data sent over the wire.

### 5. Weak Password Detection

Datasets like Have I Been Pwned's list hundreds of millions of compromised passwords. Checking "has this password ever been leaked?" against a database that size on every sign-up would be slow. A Bloom filter built over the leaked-password set answers in microseconds and fits in memory: a "definitely not compromised" answer means you can skip the full lookup.

## Implementation in C++

Here's the core class, surprisingly simple:

```cpp
#include <iostream>
#include <functional>
#include <vector>
#include <string>

using namespace std;

const int MAX_BUFF_SIZE = 1e6; // ~1MB of bits

using HashFunction = function<int(const string&)>;

class BloomFilters
{
private:
    vector<char> buffer;          // our "row of switches"
    vector<HashFunction> hashFunctions; // k hash functions

public:
    BloomFilters(int bufferSize, vector<HashFunction>& functions)
    {
        buffer.resize(bufferSize);
        hashFunctions = functions;
    }

    // O(k * |string|) — flip k bits for every insert
    void insert(const string& str) 
    {
        for (auto& func: hashFunctions) 
        {
            buffer[func(str) % buffer.size()] = 1;
        }
    }

    // O(k * |string|) — check k bits; one 0 means definitely absent
    const bool isPresent(const string& str) const
    {
        for (auto& func: hashFunctions)
        {
            if (buffer[func(str) % buffer.size()] != 1)
                return false;
        }
        return true;
    }
};
```

### Hash Functions

We need multiple hash functions that spread independently. Using different polynomial bases achieves this cheaply:

```cpp
unsigned int hashFunction1(const string& str)
{
    const int b = 31;
    unsigned int res = 0;
    for (const char& ch: str)
        res = res * b + ch;
    return res;
}

unsigned int hashFunction2(const string& str)
{
    const int b = 3727;
    unsigned int res = 0;
    for (const char& ch: str)
        res = res * b + ch - '0';
    return res;
}
```

Two hash functions with different bases (31 and 3727) produce values that are largely independent, minimizing the chance that unrelated strings collide on the same set of bits.

### Putting It Together

```cpp
int main()
{
    vector<HashFunction> functions = { hashFunction1, hashFunction2 };
    BloomFilters bf(MAX_BUFF_SIZE, functions);

    bf.insert("google.com");
    bf.insert("github.com");

    cout << bf.isPresent("google.com") << "\n"; // 1 — definitely added
    cout << bf.isPresent("evil.com")   << "\n"; // 0 — definitely NOT added
    cout << bf.isPresent("github.com") << "\n"; // 1 — definitely added

    return 0;
}
```

## Understanding False Positives

The one downside: false positives. As more elements are added, more bits get flipped to 1, and eventually a *new* element's hash positions might all land on bits already set by other elements.

The false positive probability after inserting **n** elements into a filter of **m** bits with **k** hash functions is approximately:

$$
P_{fp} \approx \left(1 - e^{-kn/m}\right)^k
$$

And the optimal number of hash functions (minimizing false positives for given m and n) is:

$$
k_{opt} = \frac{m}{n} \ln 2
$$

**A concrete example:** With 1 million bits, 100,000 inserted elements (10 bits per element) and 7 hash functions (the optimum, since 10 · ln 2 ≈ 6.9), the false positive rate is roughly **0.8%**: about one in 120 lookups for absent elements will incorrectly say "probably present."

Turning that around, the bits needed for a target false-positive rate *p* are:

$$
m = -\frac{n \ln p}{(\ln 2)^2}
$$

That is about **9.6 bits per element for 1%** and **14.4 bits per element for 0.1%**, whatever the size of the elements themselves.

The key levers you control:
- **Larger bit array** (m) → fewer false positives, more memory.
- **More hash functions** (k) → fewer false positives up to a point, then they start increasing again.
- **Fewer inserted elements** (n) → fewer false positives.

## The Fundamental Trade-off

| Property | Bloom Filter | Hash Set |
|---|---|---|
| Memory usage | Very low (bits) | High (stores full values) |
| False negatives | Never | Never |
| False positives | Possible (tunable, e.g. ~1%) | Never |
| Deletion | Not supported* | Supported |
| Lookup speed | O(k) | O(1) amortized |

\* Counting Bloom filters (and cuckoo filters) support deletion at the cost of extra space.

Use a Bloom filter when you can tolerate a small false positive rate and need to minimize memory usage. Use a regular hash set when you need exact answers and memory isn't a constraint.

## Conclusion

Bloom filters are a masterclass in practical trade-offs. By accepting a small, tunable probability of false positives, they achieve memory efficiency that traditional data structures simply can't match. The "definitely not present" guarantee is the key insight: it lets you skip expensive operations (disk reads, network calls, database queries) with absolute confidence for the common case.

Next time you browse the web safely, query a distributed database, or get article recommendations, there's a good chance a Bloom filter is quietly doing work behind the scenes.

The full implementation with additional test cases and an interactive query interface is available in my [GitHub repository](https://github.com/Jaskamalkainth/BloomFilter).

## Frequently asked questions

### Can a Bloom filter have false negatives?

No. Every inserted element sets all of its k bits, and bits are never cleared, so a lookup for an inserted element always finds all k bits set. A standard Bloom filter can only be wrong in one direction: it may report "probably present" for an element that was never added.

### How many hash functions should a Bloom filter use?

The false-positive rate is lowest when k = (m/n) · ln 2, where m is the number of bits and n the number of elements. At 10 bits per element that is about 7 hash functions, giving a false-positive rate of roughly 0.8%.

### How much memory does a Bloom filter need?

For a target false-positive rate p, the optimal size is m = −n · ln p / (ln 2)² bits, about 9.6 bits per element for 1% and 14.4 bits per element for 0.1%, no matter how large the elements themselves are.

### Can you delete elements from a Bloom filter?

Not from a standard one: clearing a bit could also remove other elements that share it and create false negatives. A counting Bloom filter replaces each bit with a small counter so deletions are possible, at the cost of several times more memory. Cuckoo filters are another option that supports deletion.

### When should I use a Bloom filter instead of a hash set?

Use a Bloom filter when memory is tight, a small false-positive rate is acceptable, and a negative answer lets you skip expensive work such as a disk read or network call. Use a hash set when you need exact answers, deletion, or the stored values themselves.


---

URL: https://jaskamalkainth.github.io/blog_posts/elasticsearchNotes.html
Title: Elasticsearch Notes: Inverted Indexes, Shards, Segments and Query DSL
Description: Elasticsearch from the bottom up: inverted indexes, Lucene shards and segments, why updates are costly, and curl examples for Query DSL, filters and aggregations.
Published: 2019-06-08
Updated: 2026-10-02

# Elasticsearch Notes

> **In short:** Elasticsearch is a distributed search and analytics engine built on Apache Lucene. An index is split into **shards**; each shard is a Lucene index made of immutable **segments**; each segment is an **inverted index** mapping terms to the documents that contain them. You talk to it with JSON over HTTP, using the Query DSL to combine scored queries, unscored filters and aggregations.

*These notes were written in 2019 against Elasticsearch 6.x. The concepts still hold, but mapping types were removed in 7.x: the URLs below such as `customer/external/1` are `customer/_doc/1` in Elasticsearch 7 and 8.*

___
Elasticsearch is a real time, search and analytics engine.
* Open-source
* High Availability - Keeps redundant data (replicas)
* Schema free - You need not know the details about your database. for ex: what does this column do? you don't care, if you use ES. :)
* Scales massively - One node running in one machine merges with other node running in other machine in the form of clusters.
* Uses RESTful API - JSON over HTTP
* Distributed multi-tenancy - If you need separate instance for an Application for every usecase. Single cluster in a DB can store many different characteristics.
* Lucene based.
* Uses _version numbers for optimistic concurrency control - every time we interact with a doc , its _version number increments. This is used to make sure that we don't miss any changes without locking.

## Elasticsearch from the Bottom up
### Inverted Indexes and Index Terms

We have a cluster of nodes in ES , within a cluster we have an ES index which spans multiple nodes through shards.
Shard is a lucene index.
Lucene is full text search library used by Elasticsearch. within a lucene index, we have segments (mini index) within segment we have,
*  *INVERTED INDEX*
     
    ``` sorted dictionary[terms]  | freq | docs   [format used to store inverted indexes]```
         
    In this sorted dictionary say we want words with ‘c’ beginning , so for this we can do binary search on it.
    now find every term containing “ours” ? (brute: all terms, which is bad)
    In other words, we can efficiently find things given term prefixes. When all we have is an inverted index, we want       everything to look like a string prefix problem. So we can do some transformations.
    * To find everything with a common suffix, we can index the reverse and we can search for everything with the common reverse(suffix).
    * To find substrings, terms are splitted into smaller terms called "n-grams". Ex: "yours" can be split into "yo", "you","our","urs","rs", this means that we could get occurrences of "ours" by searching for "our" and "urs"
    *  Geographical coordinate points such as (10.1,12.32) can be converted into "geo hashes", in this case "jkd224fk". The longer the string, the greater the precision.
    * Soundex and metaphone can be used to find strings that sound similar when pronounced out loud. Phonetic matching is enabled which uses above mentioned algorithms.
    * Lucene stores 123 as "1"-hundreds, "12"-tens and "123". Hence, searching for everything in the range[100,199] is therefore everything matching the "1"-hundreds-term. This can be done in a trie like fashion, so range searches can be done efficiently.
    * To do "Did you mean?" type searches and find spellings that are close to the input, a "Levenshtein" automaton can be built to effectively traverse the dictionary. This is too complex. 
    

### Building Indexes and Index Segments

Few factors which are important while building inverted indexes are speed, index compactness, indexing speed and update time.
Various compression techniques for ex: Delta encoding is used to minimize index sizes. Lucene does not update these small data structures. This is different from B-Trees , which can be updated.
Segments are immutable. When you delete a document , bitmap[fileremove] = 1 but the segment doesn’t change.
These Data structures are stored in segments. Lucene searches all the segments and merge the results.
Lucene also Caches all the things. Merging happens therefore indexes gets reduced by adding stuff.
when you search these shards, same as searching segments and then merge the data.
searching 1 ES Index with 2 shards is same as 2 ES index with 1 shard each.
Can’t split a shard but we can move one shard to other.
User put his doc in an Index and then that index decides in which shard to put that data. When you query for a particular doc in an index, that index searches all the shards.


>Updating a previously indexed document is a delete followed by a re-insertion of the document. Note that this means that updating a document is even more expensive than adding it in the first place. 
These indexes are built first in-memory, then occasionally flushed in segments to disk.


___

## Installation
```
brew install elasticsearch   # or run the official Docker image
```
___
## Exploring your cluster / Modifying data / Exploring Data

> The pretty parameter, again, just tells Elasticsearch to return pretty-printed JSON results.
### Cluster health
```
curl -XGET 'localhost:9200/_cat/health?v&pretty'
```
 * GET is a verb( PUT, POST, HEAD).
 * localhost is a node.
 * 9200 is HTTP port.
 * pretty is to make output easier to read.

### List nodes
```
curl -XGET 'localhost:9200/_cat/nodes?v&pretty'
```
### Create an index
```
curl -XPUT 'localhost:9200/customer?pretty&pretty'
curl -XGET 'localhost:9200/_cat/indices?v&pretty'
```
### Index and Query a Document
```
curl -XPUT 'localhost:9200/customer/external/1?pretty&pretty' -H 'Content-Type: application/json' -d'
{
  "name": "John Doe"
}'
curl -XGET 'localhost:9200/customer/external/1?pretty&pretty'
```
### Delete an Index
```
curl -XDELETE 'localhost:9200/customer?pretty&pretty'
curl -XGET 'localhost:9200/_cat/indices?v&pretty'
```
### Summary
```
curl -XPUT 'localhost:9200/customer?pretty'
curl -XPUT 'localhost:9200/customer/external/1?pretty' -H 'Content-Type: application/json' -d'
{
  "name": "John Doe"
}'
curl -XGET 'localhost:9200/customer/external/1?pretty'
curl -XDELETE 'localhost:9200/customer?pretty'
```
### Updating Documents
```
curl -XPOST 'localhost:9200/customer/external/1/_update?pretty&pretty' -H 'Content-Type: application/json' -d'
{
  "doc": { "name": "Jane Doe" }
}'
```
### Deleting Documents
```
curl -XDELETE 'localhost:9200/customer/external/2?pretty&pretty'
```
### Bulk-load a sample index (bank, 1000 docs)

```
curl -H "Content-Type: application/json" -XPOST 'localhost:9200/bank/account/_bulk?pretty&refresh' --data-binary "@accounts.json"
curl 'localhost:9200/_cat/indices?v'
```
### Query DSL

> match_all query is simply a search for all documents in the specified index ( bank ).
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match_all": {} }
}'
```

> Note that if size is not specified, it defaults to 10.
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match_all": {} },
  "size": 1
}'
```
> match_all and returns documents 11 through 20:
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match_all": {} },
  "from": 10,
  "size": 10
}'
```
>This example does a match_all and sorts the results by account balance in descending order and returns the top 10 (default size) documents.
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match_all": {} },
  "sort": { "balance": { "order": "desc" } }
}'
```
> This example shows how to return two fields, account_number and balance (inside of _source), from the search.
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match_all": {} },
  "_source": ["account_number", "balance"]
}'
```
>This example returns the account numbered 20.
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match": { "account_number": 20 } }
}'
```
>This example returns all accounts containing the term "mill" in the address.
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match": { "address": "mill" } }
}'
```
>This example is a variant of match (match_phrase) that returns all accounts containing the phrase "mill lane" in the address:
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": { "match_phrase": { "address": "mill lane" } }
}'
```
### Bool query

>This allows us to compose smaller queries into bigger queries using Boolean logic.
**must (and)** ,  **should (or)** , **must_not** clause is used.
>This example composes two match queries and returns all accounts containing "mill" and "lane" in the address:
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": {
    "bool": {
      "must": [
        { "match": { "address": "mill" } },
        { "match": { "address": "lane" } }
      ]
    }
  }
}'
```
>We can combine must, should, and must_not clauses simultaneously inside a bool query. 
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": {
    "bool": {
      "must": [
        { "match": { "age": "40" } }
      ],
      "must_not": [
        { "match": { "state": "ID" } }
      ]
    }
  }
}'
```

___

### Executing Filters

>The score is a numeric value that is a relative measure of how well the document matches the search query that we specified. The higher the score, the more relevant the document is, the lower the score, the less relevant the document is.


>Range query, which allows us to filter documents by a range of values.

```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "query": {
    "bool": {
      "must": { "match_all": {} },
      "filter": {
        "range": {
          "balance": {
            "gte": 20000,
            "lte": 30000
          }
        }
      }
    }
  }
}'
```
___

### Executing Aggregations

>Aggregations provide the ability to group and extract statistics from your data. 
```
curl -XGET 'localhost:9200/bank/_search?pretty' -H 'Content-Type: application/json' -d'
{
  "size": 0,
  "aggs": {
    "group_by_state": {
      "terms": {
        "field": "state.keyword"
      }
    }
  }
}'
```
>size = 0 means , we only want to see aggregated results.

___

### Conclusion

Till now, we've learned the basics of what Elasticsearch is and how to work with it using some of the basic REST APIs.

___

## Frequently asked questions

### What is an inverted index in Elasticsearch?

An inverted index maps each term to the list of documents that contain it, stored as a sorted term dictionary with postings (document IDs and frequencies). Because the dictionary is sorted, Lucene can find terms and term prefixes quickly instead of scanning every document.

### What is the difference between a shard and a segment?

A shard is a single Lucene index, and an Elasticsearch index is split across one or more shards that can live on different nodes. Each shard is in turn made of immutable segments, small self-contained inverted indexes that are searched together and periodically merged.

### Why is updating a document in Elasticsearch expensive?

Segments are immutable, so an update marks the old document as deleted and indexes a new copy. That costs as much as a fresh insert plus the delete, and the space is only reclaimed when segments are merged.

### What is the difference between a query and a filter in Elasticsearch?

A query (must/should) scores documents by how well they match. A filter (filter/must_not) only decides whether a document matches, without scoring, which makes it cheaper and cacheable. Range conditions such as a price or date window are usually filters.


---

URL: https://jaskamalkainth.github.io/blog_posts/korean-learning-notes.html
Title: Korean Learning Notes: Hangul, Grammar, Numbers and Verb Conjugation
Description: My Korean (한국어) study notes from Sejong Korean levels 1–2: Hangul, pronunciation rules, numbers, time, grammar and formality, vocabulary, and a 해요체 verb table.
Published: 2025-06-01
Updated: 2026-10-02

<link rel="stylesheet" href="/css/blog.css">

<div class="blog-container">
  <div class="korean-notes-header">
    <h1>한국어 학습 노트 (Korean Learning Notes)</h1>
    <p class="subtitle">My journey of learning Korean language and culture</p>
    <p class="subtitle">Class notes and a quick reference from my Sejong Korean courses: Hangul and pronunciation, native and Sino-Korean numbers, telling time, polite (해요체) verb conjugation, and everyday vocabulary.</p>
  </div>

  <div class="levels-section">
    <h2>Course Levels</h2>
    
    <div class="level-container">
      <div class="level-header" onclick="toggleLevel('level1')">
        <div class="level-info">
          <h3>🎯 Level 1 - Foundation Korean</h3>
          <div class="level-summary">
            <span class="level-status completed">✅ Completed</span>
            <span class="level-stats">13 Classes • March - June 2025</span>
          </div>
          <p class="level-description">Mastered Korean alphabet (Hangul), basic grammar, numbers, time expressions, and fundamental conversation skills including greetings, self-introduction, and daily activities.</p>
        </div>
        <div class="expand-icon" id="level1-icon">+</div>
      </div>
      
      <div class="level-content" id="level1-content">
        <div class="level-details">
          <div class="class-notes-subsection">
            <h4>📖 Reference Materials</h4>
            <div class="notes-list">
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/level1_patterns.md" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Grammar Patterns</span>
                  <span class="class-summary">Sejong Korean 1 — Grammar Patterns Summary (Units 1–12)</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/level1_vocab.md" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Vocabulary</span>
                  <span class="class-summary">Sejong Korean 1 — Vocabulary Summary (Units 1–12)</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/level1_patterns_table.md" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Quick Reference</span>
                  <span class="class-summary">Sejong Korean 1 — Grammar Patterns Quick Reference Table (Units 1–12) with Korean examples, romanization, and meanings</span>
                </div>
              </a>
            </div>
          </div>
          <div class="class-notes-subsection">
            <h4>📚 Class Notes</h4>
            <div class="notes-list">
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-03-21-Class-01.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 1</span>
                  <span class="class-date">March 21, 2025 (2025년 3월 21일)</span>
                  <span class="class-summary">Introduction to Korean alphabet (Hangul) - basic consonants and vowels created by King Sejong in 1443</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-03-28-Class-02.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 2</span>
                  <span class="class-date">March 28, 2025 (2025년 3월 28일)</span>
                  <span class="class-summary">Complex consonants, complex vowels, basic vocabulary, and Korean drinking/food culture</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-04-04-Class-03.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 3</span>
                  <span class="class-date">April 4, 2025 (2025년 4월 4일)</span>
                  <span class="class-summary">Batchim rules (final consonant sounds), consonant assimilation, Korean greetings, and food vocabulary</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-04-11-Class-04.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 4</span>
                  <span class="class-date">April 11, 2025 (2025년 4월 11일)</span>
                  <span class="class-summary">Self-introduction (이에요/예요), nationality, occupation, topic markers (은/는), and Korean home vocabulary</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-04-17-Class-05.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 5</span>
                  <span class="class-date">April 17, 2025 (2025년 4월 17일)</span>
                  <span class="class-summary">Daily activities and places, present tense verbs, three levels of formality, and Korean greeting culture</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-04-25-Class-06.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 6</span>
                  <span class="class-date">April 25, 2025 (2025년 4월 25일)</span>
                  <span class="class-summary">Locations and positions, existence (있다/없다), subject markers (이/가), and Korean festivals</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-05-09-Class-07.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 7</span>
                  <span class="class-date">May 9, 2025 (2025년 5월 9일)</span>
                  <span class="class-summary">Shopping vocabulary, Sino-Korean numbers, object markers (을/를), and months of the year</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-05-16-Class-08.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 8</span>
                  <span class="class-date">May 16, 2025 (2025년 5월 16일)</span>
                  <span class="class-summary">Days of the week, counters with Native Korean numbers, body parts, and Korean traditional clothing</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-05-23-Class-09.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 9</span>
                  <span class="class-date">May 23, 2025 (2025년 5월 23일)</span>
                  <span class="class-summary">Past tense expressions (-았어요/-었어요), location markers (에서), and Korean transportation vocabulary</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-05-30-Class-10.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 10</span>
                  <span class="class-date">May 30, 2025 (2025년 5월 30일)</span>
                  <span class="class-summary">Seasons and weather expressions, temperature reading, negation (안), and connecting words (도, 그리고)</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-06-06-Class-11.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 11</span>
                  <span class="class-date">June 6, 2025 (2025년 6월 6일)</span>
                  <span class="class-summary">Time expressions, making appointments, time markers (에), duration (부터~까지), and prohibitive forms</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-06-13-Class-12.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 12</span>
                  <span class="class-date">June 13, 2025 (2025년 6월 13일)</span>
                  <span class="class-summary">Making suggestions and appointments using -(으)ㄹ까요?, -자/-ㅂ시다, and expressing desires with -고 싶어요</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level1/2025-06-20-Class-13.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 13</span>
                  <span class="class-date">June 20, 2025 (2025년 6월 20일)</span>
                  <span class="class-summary">Weekend activities, future plans, grammar pattern: -(으)ㄹ 거예요</span>
                </div>
              </a>
            </div>
          </div>

        </div>
      </div>
    </div>

    <div class="level-container">
      <div class="level-header" onclick="toggleLevel('level2')">
        <div class="level-info">
          <h3>🚀 Level 2 - Intermediate Korean</h3>
          <div class="level-summary">
            <span class="level-status in-progress">🔄 In Progress</span>
            <span class="level-stats">18 Classes • September 2025 - April 2026</span>
          </div>
          <p class="level-description">Building on foundation knowledge to develop intermediate conversation skills, complex grammar patterns, and expanded vocabulary for daily communication.</p>
        </div>
        <div class="expand-icon" id="level2-icon">+</div>
      </div>
      
      <div class="level-content" id="level2-content">
        <div class="level-details">
          <div class="class-notes-subsection">
            <h4>📖 Reference Materials</h4>
            <div class="notes-list">
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/level2_patterns.md" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Grammar Patterns</span>
                  <span class="class-summary">Sejong Korean 2 — Grammar Patterns Summary (Units 1–14)</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/level2_vocab.md" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Vocabulary</span>
                  <span class="class-summary">Sejong Korean 2 — Vocabulary Summary (Units 1–14)</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/level2_patterns_table.md" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Quick Reference</span>
                  <span class="class-summary">Sejong Korean 2 — Grammar Patterns Quick Reference Table (Units 1–14) with Korean examples, romanization, and meanings</span>
                </div>
              </a>
            </div>
          </div>
          <div class="class-notes-subsection">
            <h4>📚 Class Notes</h4>
            <div class="notes-list">
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-09-12-Class-01.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 1</span>
                  <span class="class-date">September 12, 2025 (2025년 9월 12일)</span>
                  <span class="class-summary">Essential connecting grammar: -고 (and), 그런데 (but/however), 도 (also/too) for linking actions and adding emphasis</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-09-19-Class-02.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 2</span>
                  <span class="class-date">September 19, 2025 (2025년 9월 19일)</span>
                  <span class="class-summary">Connecting sentences (그런데), Korean counters review, text/email comprehension, and intermediate grammar patterns (에게/에게서, 때문에, 수 있어요/없어요)</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-09-26-Class-03.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 3</span>
                  <span class="class-date">September 26, 2025 (2025년 9월 26일)</span>
                  <span class="class-summary">Chapter 2: 취미 활동 (Hobby Activities) - Grammar: 못 (cannot/unable to) and -아서/어서 (because/since), hobby vocabulary, expressing abilities and reasons</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-10-17-Class-04.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 4</span>
                  <span class="class-date">October 17, 2025 (2025년 10월 17일)</span>
                  <span class="class-summary">Ch2: frequency/reason dialogues; Read&Write: 축사모 poster (Sat 7 a.m., Hana Univ) + Badminton OX (2 correct). Ch3: food ordering/taste; dialogues (ordering, preference); grammar: -(으)ㄹ래요, 무슨+N, 그러면/그런데/그래서; vocab: core dishes & taste adjectives.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-10-31-Class-05.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 5</span>
                  <span class="class-date">October 31, 2025 (2025년 10월 31일)</span>
                  <span class="class-summary">Chapter 3: Menu ordering, Read &amp; Write poster, restaurant intro.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-11-07-Class-06.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 6</span>
                  <span class="class-date">November 7, 2025 (2025년 11월 7일)</span>
                  <span class="class-summary">CHAPTER: 교통 (Transportation) - Grammar: 이/가 걸리다 (it takes [time]), …에서 …까지 (from … to …); Vocabulary: transportation modes and verbs; Dialogues: asking how you go/come, directions with transfers; Practice: durations (얼마나 … 걸려요/걸렸어요), routes, commute talk.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-11-14-Class-07.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 7</span>
                  <span class="class-date">November 14, 2025 (2025년 11월 14일)</span>
                  <span class="class-summary">CHAPTER: 교통 (Transportation) - Grammar: …에서 …까지, [교통수단]을/를 타고 가다/오다/다니다, 갈아타다, 내리다, (시간)이/가 걸리다, -(으)세요; Practice: transfer routes, where to get off, durations; Read &amp; Write: Airport→city table, Beijing→hometown reading; Vocab: transportation/route words and common places.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-11-28-Class-08.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 8</span>
                  <span class="class-date">November 28, 2025 (2025년 11월 28일)</span>
                  <span class="class-summary">CHAPTER: 길 찾기 (Finding the way) - Grammar: (으)로 (toward/into/by), -아서/어서 (sequence); Actions: 건너다/지나다, 들어가다/나오다/올라가다/내려가다; Patterns: 오른쪽/왼쪽(으)로, 똑바로(쭉) 가세요; Tasks: "오시는 길" style directions.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-12-05-Class-09.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 9</span>
                  <span class="class-date">December 5, 2025 (2025년 12월 5일)</span>
                  <span class="class-summary">Theme: 회사생활 (Office life) - Vocab: 출근/퇴근, 근무시간, 회의, 제안서/서류, 첨부/복사/출력, 동료, 쉬는 시간, 점심; Patterns: -(으)면서, -(으)면 돼요, -(으)세요, -아서/어서; Practice: Q&amp;A and office verb examples.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2025-12-12-Class-10.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 10</span>
                  <span class="class-date">December 12, 2025 (2025년 12월 12일)</span>
                  <span class="class-summary">Chapter 5 wrap-up - Integrated directions practice using (으)로 and -아서/어서; Read &amp; Write: "오시는 길" poster, email directions; Speaking: 위치 묻고 답하기, 집 찾아오는 안내 편지 쓰기; Vocab: 이동 동사, 방향어, 장소.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-01-09-Class-12.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 12</span>
                  <span class="class-date">January 9, 2026 (2026년 1월 9일)</span>
                  <span class="class-summary">Chapter 6 - 전화 (Phone calls): ask/give phone numbers, make calls; Grammar: -아/어 주다 (do for someone), -지요 (confirmation); Vocab: phone/text/call expressions.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-01-16-Class-13.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 13</span>
                  <span class="class-date">January 16, 2026 (2026년 1월 16일)</span>
                  <span class="class-summary">Chapter 6 wrap-up - phone conversation practice and application; Activities: role-plays (asking numbers, calling offices), comprehension (texts/emails), writing about phone usage; Vocab: Chapter 6 review.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-01-23-Class-14.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 14</span>
                  <span class="class-date">January 23, 2026 (2026년 1월 23일)</span>
                  <span class="class-summary">Chapter 7 - 외모 (Appearance): describe appearance and clothing; Grammar: -(으)ㄴ (adjective modifier), -고 있다 (wearing/current state); Vocab: 외모, 옷차림.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-01-23-Class-15.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 15</span>
                  <span class="class-date">January 23, 2026 (2026년 1월 23일)</span>
                  <span class="class-summary">Chapter 8 — 가족 (Family): introducing family, asking and answering about family; Grammar: 의 (possession), -(으)시- (honorific); Vocab: 가족, 존대 표현.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-02-13-Class-16.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 16</span>
                  <span class="class-date">February 13, 2026 (2026년 2월 13일)</span>
                  <span class="class-summary">Chapter 8 — 가족 (Family) Part 2: reading tables and short texts, writing family introductions, practice with 직업/취미/외모.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-02-20-Class-17.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 17</span>
                  <span class="class-date">February 20, 2026 (2026년 2월 20일)</span>
                  <span class="class-summary">Chapter 9 — Part 2.</span>
                </div>
              </a>
              <a href="https://github.com/Jaskamalkainth/korean-language-learning-notes/blob/main/level2/2026-02-27-Class-18.txt" target="_blank" class="note-item">
                <div class="note-content">
                  <span class="class-number">Class 18</span>
                  <span class="class-date">February 27, 2026 (2026년 2월 27일)</span>
                  <span class="class-summary">Class 18 notes (YT Video).</span>
                </div>
              </a>
            </div>
          </div>

        </div>
      </div>
    </div>
  </div>

  <div class="cultural-content-section">
    <h2>Cultural Videos & Songs from Classes</h2>
    
    <div class="cultural-grid">
      <div class="cultural-card">
        <h3>📺 Culture Videos</h3>
        <div class="video-links">
          <a href="https://www.youtube.com/watch?v=1K6Spf_JmQc" target="_blank" class="video-link">
            <span class="video-title">Class 3 - Korean Language & Culture Series (Ep.3: Korean Food)</span>
          </a>
          <a href="https://www.youtube.com/watch?v=l-trIfHnbBs" target="_blank" class="video-link">
            <span class="video-title">Class 4 - Korean Language & Culture Series (Ep.4: Korean Homes)</span>
          </a>
          <a href="https://www.youtube.com/watch?v=Q4J7uylaOLA" target="_blank" class="video-link">
            <span class="video-title">Class 5 - Korean Language & Culture Series (Ep.1: Korean Greetings)</span>
          </a>
          <a href="https://www.youtube.com/watch?v=RCBtMJZCGRE" target="_blank" class="video-link">
            <span class="video-title">Class 6 - Korean Language & Culture Series (Ep.5: Korean Holidays)</span>
          </a>
          <a href="https://www.youtube.com/watch?v=Up1Bd7hoLO0" target="_blank" class="video-link">
            <span class="video-title">Class 8 - Korean Language & Culture Series (Ep.7: Korean Attire)</span>
          </a>
          <a href="https://www.youtube.com/watch?v=PQjxB1iAH2I" target="_blank" class="video-link">
            <span class="video-title">Class 9 - Korean Language & Culture Series (Ep.6: Korean Transportation)</span>
          </a>
          <a href="https://www.youtube.com/watch?v=bjMf6r4KI80" target="_blank" class="video-link">
            <span class="video-title">Class 10 - Korean Phrases 5: Describing the Weather</span>
          </a>
          <a href="https://www.youtube.com/watch?v=uRvvbTD5cIw" target="_blank" class="video-link">
            <span class="video-title">Class 10 - Korean Dialogue Listening</span>
          </a>
          <a href="https://www.youtube.com/watch?v=xYli4WL_Zsg" target="_blank" class="video-link">
            <span class="video-title">Class 11 - Daily Routine Phrases</span>
          </a>
          <a href="https://www.youtube.com/watch?v=096Ix_ueCZo" target="_blank" class="video-link">
            <span class="video-title">Class 11 - Role Play Video</span>
          </a>
        </div>
      </div>

      <div class="cultural-card">
        <h3>🎵 Korean Songs & Poems</h3>
        <div class="songs-content">
          <div class="song-item">
            <h4>Korean Happy Birthday Song</h4>
            <div class="lyrics">
              <div class="lyric-line">생일 축하합니다 <em>(saengil chukahamnida)</em> - Happy birthday to you</div>
              <div class="lyric-line">사랑하는 (name) 씨 <em>(saranghaneun ... ssi)</em> - Dear (name)</div>
            </div>
          </div>

          <div class="song-item">
            <h4>Three Bears Song (곰 세 마리)</h4>
            <div class="lyrics">
              <div class="lyric-line">곰 세 마리가 한 집에 있어 <em>(gom se mariga han jibe isseo)</em></div>
              <div class="lyric-translation">Three bears are in one house</div>
              <div class="lyric-line">아빠 곰은 뚱뚱해 <em>(appa gomeun ttungttunghae)</em></div>
              <div class="lyric-translation">Daddy bear is fat</div>
              <div class="lyric-line">엄마 곰은 날씬해 <em>(eomma gomeun nalssinhae)</em></div>
              <div class="lyric-translation">Mommy bear is slim</div>
              <div class="lyric-line">애기 곰은 너무 귀여워 <em>(aegi gomeun neomu gwiyeowo)</em></div>
              <div class="lyric-translation">Baby bear is very cute</div>
              <div class="lyric-line">으쓱 으쓱 잘한다 <em>(eusseuk eusseuk jalhanda)</em></div>
              <div class="lyric-translation">Wiggle wiggle well done!</div>
            </div>
          </div>

          <div class="song-item">
            <h4>Twinkle Little Star (반짝 반짝 작은 별)</h4>
            <div class="lyrics">
              <a href="https://www.youtube.com/watch?v=vp-ZsZ28li4" target="_blank" class="video-link">
                <span class="video-title">🎬 Class 10 - Watch Korean Nursery Song</span>
              </a>
            </div>
          </div>
          <div class="song-item">
            <h4>Head Shoulders Knees and Toes</h4>
            <div class="lyrics">
              <a href="https://www.youtube.com/watch?v=YMUBFumKXHA" target="_blank" class="video-link">
                <span class="video-title">🎬 Korean & EnglishㅣWekiz Songs for Children</span>
              </a>
            </div>
          </div>

          <div class="song-item">
            <h4>Unity Haiku (통일 하이쿠)</h4>
            <div class="lyrics">
              <div class="korean-poem">
                <div class="lyric-line">우리 이름이 달라도</div>
                <div class="lyric-line">우리는 같은 하늘 아래 살아요</div>
                <div class="lyric-line">우리는 하나예요 <span class="inline-author">- JK</span></div>
              </div>
              <div class="poem-explanation">
                <em> Though our names, cultures, religions, and countries may differ, we all live under the same sky and are one.</em>
              </div>
            </div>
          </div>
      </div>
    </div>
  </div>

  <div class="quick-reference-section">
    <h2>Quick Reference</h2>
    
    <div class="reference-grid">
      <div class="reference-card">
        <h3>한글 (Hangul)</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Basic Vowels:</strong>
            <div class="compact-content">
              <div class="compact-item">ㅏ (a)</div>
              <div class="compact-item">ㅛ (yo)</div>
              <div class="compact-item">ㅑ (ya)</div>
              <div class="compact-item">ㅜ (u)</div>
              <div class="compact-item">ㅓ (eo)</div>
              <div class="compact-item">ㅠ (yu)</div>
              <div class="compact-item">ㅕ (yeo)</div>
              <div class="compact-item">ㅡ (eu)</div>
              <div class="compact-item">ㅗ (o)</div>
              <div class="compact-item">ㅣ (i)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Basic Consonants:</strong>
            <div class="compact-content">
              <div class="compact-item">ㄱ (g/k)</div>
              <div class="compact-item">ㅈ (j)</div>
              <div class="compact-item">ㄴ (n)</div>
              <div class="compact-item">ㅊ (ch)</div>
              <div class="compact-item">ㄷ (d/t)</div>
              <div class="compact-item">ㅋ (k)</div>
              <div class="compact-item">ㄹ (r/l)</div>
              <div class="compact-item">ㅌ (t)</div>
              <div class="compact-item">ㅁ (m)</div>
              <div class="compact-item">ㅍ (p)</div>
              <div class="compact-item">ㅂ (b/p)</div>
              <div class="compact-item">ㅎ (h)</div>
              <div class="compact-item">ㅅ (s)</div>
              <div class="compact-item">ㅇ (silent/ng)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Complex Consonants:</strong>
            <div class="compact-content">
              <div class="compact-item">ㄲ (kk)</div>
              <div class="compact-item">ㅆ (ss)</div>
              <div class="compact-item">ㄸ (tt)</div>
              <div class="compact-item">ㅉ (jj)</div>
              <div class="compact-item">ㅃ (pp)</div>
              <div class="compact-item"><em>Stronger than basic</em></div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Complex Vowels:</strong>
            <div class="compact-content">
              <div class="compact-item">ㅐ (ae - like "care")</div>
              <div class="compact-item">ㅝ (wo - like "wonder")</div>
              <div class="compact-item">ㅒ (yae - like "yam")</div>
              <div class="compact-item">ㅞ (we - like "wedding")</div>
              <div class="compact-item">ㅔ (e - like "bed")</div>
              <div class="compact-item">ㅟ (wi - like "week")</div>
              <div class="compact-item">ㅖ (ye - like "yes")</div>
              <div class="compact-item">ㅢ (ui - like "gooey")</div>
              <div class="compact-item">ㅘ (wa - like "water")</div>
              <div class="compact-item">ㅙ (wae - like "wet")</div>
              <div class="compact-item">ㅚ (oe - like "wet")</div>
              <div class="compact-item"></div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Pronunciation Rules</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Batchim Rules:</strong>
            <div class="compact-content">
              <div class="compact-item">ㄱ,ㅋ,ㄲ → [k] (수박=su-bak)</div>
              <div class="compact-item">ㅁ → [m] (밤=bam)</div>
              <div class="compact-item">ㄴ → [n] (안=an)</div>
              <div class="compact-item">ㅂ,ㅍ → [p] (집=jip)</div>
              <div class="compact-item">ㄷ,ㅅ,ㅆ,ㅈ,ㅊ,ㅌ,ㅎ → [t] (옷=ot)</div>
              <div class="compact-item">ㅇ → [ng] (공=gong)</div>
              <div class="compact-item">ㄹ → [l] (달=dal)</div>
              <div class="compact-item"></div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Assimilation:</strong>
            <div class="compact-content">
              <div class="compact-item">ㅂ+ㄴ → [m-n] (입니다→[임니다])</div>
              <div class="compact-item">같이 → [가치] (ga-chi=together)</div>
            </div>
          </div>
          <div class="compact-row">
            ㅎ Neutralization:
            <div class="compact-content">
              <div class="compact-item">Final position: silent (좋다→[조타])</div>
              <div class="compact-item">Before consonants: silent (않고→[안꼬])</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Double Batchim:</strong>
            <div class="compact-content">
              <div class="compact-item">Word end/before consonant: one consonant</div>
              <div class="compact-item">Before vowel: second moves to next syllable</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Numbers</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Sino-Korean (dates, money, minutes, years, phone numbers, addresses, mathematical calculations):</strong>
            <div class="compact-content">
              <div class="compact-item">일 (il - 1)</div>
              <div class="compact-item">십 (sip - 10)</div>
              <div class="compact-item">이 (i - 2)</div>
              <div class="compact-item">백 (baek - 100)</div>
              <div class="compact-item">삼 (sam - 3)</div>
              <div class="compact-item">천 (cheon - 1K)</div>
              <div class="compact-item">사 (sa - 4)</div>
              <div class="compact-item">만 (man - 10K)</div>
              <div class="compact-item">오 (o - 5)</div>
              <div class="compact-item">억 (eok - 100M)</div>
              <div class="compact-item">육 (yuk - 6)</div>
              <div class="compact-item">조 (jo - 1T)</div>
              <div class="compact-item">칠 (chil - 7)</div>
              <div class="compact-item"></div>
              <div class="compact-item">팔 (pal - 8)</div>
              <div class="compact-item"></div>
              <div class="compact-item">구 (gu - 9)</div>
              <div class="compact-item"></div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Native Korean (counting objects, people, animals, hours 1-12, age, ordering food/drinks):</strong>
            <div class="compact-content">
              <div class="compact-item">하나 (hana - 1)</div>
              <div class="compact-item">열 (yeol - 10)</div>
              <div class="compact-item">둘 (dul - 2)</div>
              <div class="compact-item">열하나 (yeol hana - 11)</div>
              <div class="compact-item">셋 (set - 3)</div>
              <div class="compact-item">스물 (seumul - 20)</div>
              <div class="compact-item">넷 (net - 4)</div>
              <div class="compact-item">서른 (seoreun - 30)</div>
              <div class="compact-item">다섯 (daseot - 5)</div>
              <div class="compact-item">마흔 (maheun - 40)</div>
              <div class="compact-item">여섯 (yeoseot - 6)</div>
              <div class="compact-item">쉰 (swin - 50)</div>
              <div class="compact-item">일곱 (ilgop - 7)</div>
              <div class="compact-item">예순 (yesun - 60)</div>
              <div class="compact-item">여덟 (yeodeol - 8)</div>
              <div class="compact-item">일흔 (ilheun - 70)</div>
              <div class="compact-item">아홉 (ahop - 9)</div>
              <div class="compact-item">여든 (yeodeun - 80)</div>
              <div class="compact-item"></div>
              <div class="compact-item">아흔 (aheun - 90)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Time</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Months:</strong>
            <div class="compact-content">
              <div class="compact-item">1월 (irwol - Jan)</div>
              <div class="compact-item">7월 (chirwol - Jul)</div>
              <div class="compact-item">2월 (iwol - Feb)</div>
              <div class="compact-item">8월 (palwol - Aug)</div>
              <div class="compact-item">3월 (samwol - Mar)</div>
              <div class="compact-item">9월 (guwol - Sep)</div>
              <div class="compact-item">4월 (sawol - Apr)</div>
              <div class="compact-item">10월 (siwol - Oct)</div>
              <div class="compact-item">5월 (owol - May)</div>
              <div class="compact-item">11월 (sibil-wol - Nov)</div>
              <div class="compact-item">6월 (yuwol - Jun)</div>
              <div class="compact-item">12월 (sibi-wol - Dec)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Days:</strong>
            <div class="compact-content">
              <div class="compact-item">월요일 (wol-yoil - Monday/Moon)</div>
              <div class="compact-item">금요일 (geum-yoil - Friday/Gold)</div>
              <div class="compact-item">화요일 (hwa-yoil - Tuesday/Fire)</div>
              <div class="compact-item">토요일 (to-yoil - Saturday/Earth)</div>
              <div class="compact-item">수요일 (su-yoil - Wednesday/Water)</div>
              <div class="compact-item">일요일 (il-yoil - Sunday/Sun)</div>
              <div class="compact-item">목요일 (mok-yoil - Thursday/Wood)</div>
              <div class="compact-item"></div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Time Format:</strong>
            <div class="compact-content">
              <div class="compact-item">오전 (ojeon - AM)</div>
              <div class="compact-item">분 (bun - minute)</div>
              <div class="compact-item">오후 (ohu - PM)</div>
              <div class="compact-item">시 (si - used after hour)</div>
              <div class="compact-item">시간 (sigan - hour)</div>
              <div class="compact-item"></div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Examples:</strong>
            <div class="compact-content">
              <div class="compact-item">3:05 PM → 오후 세 시 오 분</div>
              <div class="compact-item">12:00 PM → 오후 열두 시</div>
              <div class="compact-item">9:30 AM → 오전 아홉 시 삼십 분</div>
              <div class="compact-item"><em>Note: Native Korean for hours, Sino-Korean for minutes</em></div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Grammar & Formality</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Markers:</strong>
            <div class="compact-content">
              <div class="compact-item">이/가 (i/ga - subject: consonant+이, vowel+가)</div>
              <div class="compact-item">을/를 (eul/reul - object: consonant+을, vowel+를)</div>
              <div class="compact-item">은/는 (eun/neun - topic: consonant+은, vowel+는)</div>
              <div class="compact-item">에 (e - location/time marker for places and times)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Formality Levels:</strong>
            <div class="compact-content">
              <div class="compact-item">반말 (banmal - casual: no ending or -아/어)</div>
              <div class="compact-item">-습니다/-습니까 (seumnida/seumnikka - formal)</div>
              <div class="compact-item">-요 (polite ending)</div>
              <div class="compact-item">-십니다/-십니까 (simnida/simnikka - highest)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Essential Vocabulary</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Greetings:</strong>
            <div class="compact-content">
              <div class="compact-item">안녕하세요 (annyeonghaseyo - hello)</div>
              <div class="compact-item">안녕히 가세요 (annyeonghi gaseyo - goodbye to leaving)</div>
              <div class="compact-item">안녕히 계세요 (annyeonghi gyeseyo - goodbye when you leave)</div>
              <div class="compact-item">환영합니다 (hwanyeonghamnida - welcome)</div>
              <div class="compact-item">감사합니다 (kamsahamnida - thank you)</div>
              <div class="compact-item">고맙습니다 (gomapseumnida - thank you polite)</div>
              <div class="compact-item">만나서 반갑습니다 (mannaseo bangapseumnida - nice to meet you)</div>
              <div class="compact-item">처음 뵙겠습니다 (cheoeum boepgetseumnida - nice to meet you humble)</div>
              <div class="compact-item">죄송합니다 (joesonghamnida - I'm sorry)</div>
              <div class="compact-item">미안해요 (mianhaeyo - I'm sorry informal)</div>
              <div class="compact-item">밥 먹었어요? (bap meogeosseoyo - have you eaten?)</div>
              <div class="compact-item">식사하셨어요? (siksahasyeosseoyo - have you eaten honorific)</div>
              <div class="compact-item">잠시만요 (jamsimanyo - excuse me)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Classroom:</strong>
            <div class="compact-content">
              <div class="compact-item">책을 펴세요 (chaegeul pyeoseyo - open book)</div>
              <div class="compact-item">알겠어요? (algesseoyo - understand?)</div>
              <div class="compact-item">책을 보세요 (chaegeul boseyo - look at book)</div>
              <div class="compact-item">네 알겠어요 (ne algesseoyo - yes I understand)</div>
              <div class="compact-item">잘 들으세요 (jal deureuseyo - listen carefully)</div>
              <div class="compact-item">아니요 모르겠어요 (aniyo moreugesseoyo - no I don't understand)</div>
              <div class="compact-item">따라 하세요 (ttara haseyo - repeat after me)</div>
              <div class="compact-item">질문 있어요? (jilmun isseoyo - any questions?)</div>
              <div class="compact-item">읽으세요 (ilgeuseyo - read it)</div>
              <div class="compact-item">질문하세요 (jilmun haseyo - ask question)</div>
              <div class="compact-item">쓰세요 (sseuseyo - write it)</div>
              <div class="compact-item">대답하세요 (daedap haseyo - answer question)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Verb Conjugations</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Present Tense Polite (-요):</strong>
            <div class="compact-content">
              <div class="compact-item">가다 → 가요 (gada → gayo - go)</div>
              <div class="compact-item">오다 → 와요 (oda → wayo - come)</div>
              <div class="compact-item">보다 → 봐요 (boda → bwayo - see/watch)</div>
              <div class="compact-item">먹다 → 먹어요 (meokda → meogeoyo - eat)</div>
              <div class="compact-item">마시다 → 마셔요 (masida → masyeoyo - drink)</div>
              <div class="compact-item">하다 → 해요 (hada → haeyo - do)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Past Tense (-았어요/-었어요):</strong>
            <div class="compact-content">
              <div class="compact-item">갔어요 (gasseoyo - went)</div>
              <div class="compact-item">왔어요 (wasseoyo - came)</div>
              <div class="compact-item">봤어요 (bwasseoyo - saw/watched)</div>
              <div class="compact-item">먹었어요 (meogeosseoyo - ate)</div>
              <div class="compact-item">마셨어요 (masyeosseoyo - drank)</div>
              <div class="compact-item">했어요 (haesseoyo - did)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Suggestions & Requests:</strong>
            <div class="compact-content">
              <div class="compact-item">갈까요? (galkkayo - shall we go?)</div>
              <div class="compact-item">가세요 (gaseyo - please go)</div>
              <div class="compact-item">가고 싶어요 (gago sipeoyo - I want to go)</div>
              <div class="compact-item">가지 마세요 (gaji maseyo - please don't go)</div>
              <div class="compact-item">안 가요 (an gayo - won't go by choice)</div>
              <div class="compact-item">못 가요 (mot gayo - can't go due to circumstances)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Question Words & Useful Expressions</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Question Words:</strong>
            <div class="compact-content">
              <div class="compact-item">뭐 (mwo - what)</div>
              <div class="compact-item">어디 (eodi - where)</div>
              <div class="compact-item">언제 (eonje - when)</div>
              <div class="compact-item">몇 시 (myeot si - what time)</div>
              <div class="compact-item">무슨 요일 (museun yoil - what day)</div>
              <div class="compact-item">몇 개 (myeot gae - how many items)</div>
              <div class="compact-item">얼마 (eolma - how much)</div>
              <div class="compact-item">어떻게 (eotteoke - how)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Daily Expressions:</strong>
            <div class="compact-content">
              <div class="compact-item">무엇을 드릴까요? (mueoseul deurilkkayo - may I help you)</div>
              <div class="compact-item">얼마예요? (eolmayeyo - how much is it)</div>
              <div class="compact-item">어떻게 지내세요? (eotteoke jinaeseyo - how are you)</div>
              <div class="compact-item">어때요? (eottaeyo - how about it)</div>
              <div class="compact-item">좋아요 (joayo - good/sounds good)</div>
              <div class="compact-item">괜찮아요 (gwaenchanhayo - it's okay)</div>
              <div class="compact-item">잘 먹겠습니다 (jal meokgetseumnida - before eating)</div>
              <div class="compact-item">잘 먹었습니다 (jal meogeotseumnida - after eating)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Transportation & Places</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Transportation:</strong>
            <div class="compact-content">
              <div class="compact-item">버스 (beoseu - bus)</div>
              <div class="compact-item">지하철 (jihacheol - subway)</div>
              <div class="compact-item">택시 (taeksi - taxi)</div>
              <div class="compact-item">KTX (keiteekseu - high-speed rail)</div>
              <div class="compact-item">버스 정류장 (beoseu jeongryujang - bus stop)</div>
              <div class="compact-item">지하철역 (jihacheoryeok - subway station)</div>
              <div class="compact-item">교통 카드 (gyotong kadeu - transportation card)</div>
              <div class="compact-item">운전하다 (unjeonhada - to drive)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>More Places:</strong>
            <div class="compact-content">
              <div class="compact-item">영화관 (yeonghwagwan - movie theater)</div>
              <div class="compact-item">도서관 (doseogwan - library)</div>
              <div class="compact-item">백화점 (baekhwajeom - department store)</div>
              <div class="compact-item">카페 (kape - café)</div>
              <div class="compact-item">교실 (gyosil - classroom)</div>
              <div class="compact-item">회의실 (hoeuisil - meeting room)</div>
              <div class="compact-item">병원 (byeongwon - hospital)</div>
              <div class="compact-item">은행 (eunhaeng - bank)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Currency & Business</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Money:</strong>
            <div class="compact-content">
              <div class="compact-item">원 (won - Korean currency)</div>
              <div class="compact-item">천원 (cheonwon - 1,000 won)</div>
              <div class="compact-item">만원 (manwon - 10,000 won)</div>
              <div class="compact-item">지폐 (jipye - banknote)</div>
              <div class="compact-item">동전 (dongjeon - coin)</div>
              <div class="compact-item">신용카드 (sinyongkadeu - credit card)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Business Terms:</strong>
            <div class="compact-content">
              <div class="compact-item">회사 이름 (hoesa ireum - company name)</div>
              <div class="compact-item">이름 (ireum - name)</div>
              <div class="compact-item">전화번호 (jeonhwabeonho - phone number)</div>
              <div class="compact-item">이메일 (imeil - email)</div>
              <div class="compact-item">주소 (juso - address)</div>
              <div class="compact-item">회의 (hoeui - meeting)</div>
              <div class="compact-item">약속 (yaksok - appointment)</div>
              <div class="compact-item">시간이 있다/없다 (sigani itda/eopda - have/don't have time)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Korean Holidays & Culture</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Major Holidays:</strong>
            <div class="compact-content">
              <div class="compact-item">설날 (seollal - Lunar New Year)</div>
              <div class="compact-item">추석 (chuseok - Harvest Festival)</div>
              <div class="compact-item">한글날 (hangeulnal - Hangul Day Oct 9)</div>
              <div class="compact-item">어린이날 (eorininal - Children's Day May 5)</div>
              <div class="compact-item">어버이날 (eobeoinal - Parents Day May 8)</div>
              <div class="compact-item">광복절 (gwangbokjeol - Liberation Day Aug 15)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Traditional Foods:</strong>
            <div class="compact-content">
              <div class="compact-item">떡국 (tteokguk - rice cake soup for New Year)</div>
              <div class="compact-item">송편 (songpyeon - half-moon rice cakes for Chuseok)</div>
              <div class="compact-item">전 (jeon - savory pancakes)</div>
              <div class="compact-item">갈비탕 (galbitang - beef short rib soup)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Cultural Terms:</strong>
            <div class="compact-content">
              <div class="compact-item">세배 (sebae - deep bow to elders)</div>
              <div class="compact-item">세뱃돈 (sebaetdon - New Year money gift)</div>
              <div class="compact-item">한류 (hallyu - Korean Wave)</div>
              <div class="compact-item">차례 (charye - ancestor memorial service)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Counters & Nationalities</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Counters:</strong>
            <div class="compact-content">
              <div class="compact-item">개 (gae - general item)</div>
              <div class="compact-item">권 (gwon - book)</div>
              <div class="compact-item">병 (byeong - bottle)</div>
              <div class="compact-item">장 (jang - flat object/paper/tickets)</div>
              <div class="compact-item">명 (myeong - person formal)</div>
              <div class="compact-item">마리 (mari - animal)</div>
              <div class="compact-item">사람 (saram - person informal)</div>
              <div class="compact-item"></div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Nationalities:</strong>
            <div class="compact-content">
              <div class="compact-item">한국 사람 (hanguk saram - Korean)</div>
              <div class="compact-item">미국 사람 (miguk saram - American)</div>
              <div class="compact-item">일본 사람 (ilbon saram - Japanese)</div>
              <div class="compact-item">중국 사람 (jungguk saram - Chinese)</div>
              <div class="compact-item">프랑스 사람 (peurangseu saram - French)</div>
              <div class="compact-item">독일 사람 (dogil saram - German)</div>
              <div class="compact-item">호주 사람 (hoju saram - Australian)</div>
              <div class="compact-item">베트남 사람 (beteunam saram - Vietnamese)</div>
              <div class="compact-item">파키스탄 사람 (pakiseutan saram - Pakistani)</div>
              <div class="compact-item">몽골 사람 (monggol saram - Mongolian)</div>
              <div class="compact-item">아일랜드 사람 (aillaendeu saram - Irish)</div>
              <div class="compact-item">러시아 사람 (reosia saram - Russian)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Occupations & Activities</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Jobs:</strong>
            <div class="compact-content">
              <div class="compact-item">의사 (uisa - doctor)</div>
              <div class="compact-item">선생님 (seonsaengnim - teacher)</div>
              <div class="compact-item">경찰 (gyeongchal - police officer)</div>
              <div class="compact-item">간호사 (ganhosa - nurse)</div>
              <div class="compact-item">공무원 (gongmuwon - civil servant)</div>
              <div class="compact-item">변호사 (byeonhosa - lawyer)</div>
              <div class="compact-item">회사원 (hoesawon - office worker)</div>
              <div class="compact-item">학생 (haksaeng - student)</div>
              <div class="compact-item">기사/운전사 (gisa/unjeonsa - driver)</div>
              <div class="compact-item">기자 (gija - reporter)</div>
              <div class="compact-item">요리사 (yorisa - chef)</div>
              <div class="compact-item">가수 (gasu - singer)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Common Activities:</strong>
            <div class="compact-content">
              <div class="compact-item">공부하다 (gongbuhada - to study)</div>
              <div class="compact-item">일하다 (ilhada - to work)</div>
              <div class="compact-item">운동하다 (undonghada - to exercise)</div>
              <div class="compact-item">전화하다 (jeonhwahada - to call)</div>
              <div class="compact-item">이야기하다 (iyagihada - to talk)</div>
              <div class="compact-item">요리하다 (yorihada - to cook)</div>
              <div class="compact-item">쇼핑하다 (syopinghada - to shop)</div>
              <div class="compact-item">운전하다 (unjeonhada - to drive)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Food & Shopping</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Korean Food:</strong>
            <div class="compact-content">
              <div class="compact-item">김밥 (gimbap - seaweed rice rolls)</div>
              <div class="compact-item">비빔밥 (bibimbap - mixed rice dish)</div>
              <div class="compact-item">볶음밥 (bokkeumbap - fried rice)</div>
              <div class="compact-item">라면 (ramyeon - ramen noodles)</div>
              <div class="compact-item">떡볶이 (tteokbokki - spicy rice cakes)</div>
              <div class="compact-item">삼겹살 (samgyeopsal - pork belly)</div>
              <div class="compact-item">치킨 (chikin - chicken)</div>
              <div class="compact-item">호떡 (hotteok - sweet pancake)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Drinks & Items:</strong>
            <div class="compact-content">
              <div class="compact-item">소주 (soju - Korean alcoholic drink)</div>
              <div class="compact-item">막걸리 (makgeolli - rice wine)</div>
              <div class="compact-item">우유 (uyu - milk)</div>
              <div class="compact-item">커피 (keopi - coffee)</div>
              <div class="compact-item">물 (mul - water)</div>
              <div class="compact-item">주스 (juseu - juice)</div>
              <div class="compact-item">사과 (sagwa - apple)</div>
              <div class="compact-item">수박 (subak - watermelon)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Condiments:</strong>
            <div class="compact-content">
              <div class="compact-item">된장 (doenjang - soybean paste)</div>
              <div class="compact-item">고추장 (gochujang - red chili paste)</div>
              <div class="compact-item">간장 (ganjang - soy sauce)</div>
              <div class="compact-item">쌈장 (ssamjang - thick soybean paste)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Body Parts & Position Words</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Head/Face:</strong>
            <div class="compact-content">
              <div class="compact-item">머리 (meori - head)</div>
              <div class="compact-item">머리카락 (meorikarak - hair)</div>
              <div class="compact-item">얼굴 (eolgul - face)</div>
              <div class="compact-item">눈 (nun - eyes)</div>
              <div class="compact-item">코 (ko - nose)</div>
              <div class="compact-item">입 (ip - mouth)</div>
              <div class="compact-item">귀 (gwi - ears)</div>
              <div class="compact-item">목 (mok - neck)</div>
              <div class="compact-item">이마 (ima - forehead)</div>
              <div class="compact-item">턱 (teok - chin)</div>
              <div class="compact-item">입술 (ipsul - lips)</div>
              <div class="compact-item">이 (i - teeth)</div>
              <div class="compact-item">혀 (hyeo - tongue)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Body:</strong>
            <div class="compact-content">
              <div class="compact-item">손 (son - hand)</div>
              <div class="compact-item">팔 (pal - arm)</div>
              <div class="compact-item">다리 (dari - leg)</div>
              <div class="compact-item">발 (bal - foot)</div>
              <div class="compact-item">어깨 (eokkae - shoulder)</div>
              <div class="compact-item">무릎 (mureup - knee)</div>
              <div class="compact-item">허리 (heori - waist)</div>
              <div class="compact-item">가슴 (gaseum - chest)</div>
              <div class="compact-item">배 (bae - stomach/abdomen)</div>
              <div class="compact-item">등 (deung - back)</div>
              <div class="compact-item">손가락 (songarak - finger)</div>
              <div class="compact-item">발가락 (balgarak - toe)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Position Words:</strong>
            <div class="compact-content">
              <div class="compact-item">앞 (ap - front)</div>
              <div class="compact-item">뒤 (dwi - back/behind)</div>
              <div class="compact-item">옆 (yeop - next to)</div>
              <div class="compact-item">위 (wi - above/on)</div>
              <div class="compact-item">아래/밑 (arae/mit - below/under)</div>
              <div class="compact-item">안 (an - inside)</div>
              <div class="compact-item">밖 (bak - outside)</div>
              <div class="compact-item">사이 (sai - between)</div>
              <div class="compact-item">가운데 (gaunde - middle/center)</div>
              <div class="compact-item">오른쪽 (oreunjjok - right)</div>
              <div class="compact-item">왼쪽 (oenjjok - left)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card">
        <h3>Weather & Traditional</h3>
        <div class="reference-content">
          <div class="compact-row">
            <strong>Seasons & Weather:</strong>
            <div class="compact-content">
              <div class="compact-item">봄 (bom - spring)</div>
              <div class="compact-item">여름 (yeoreum - summer)</div>
              <div class="compact-item">가을 (gaeul - fall/autumn)</div>
              <div class="compact-item">겨울 (gyeoul - winter)</div>
              <div class="compact-item">덥다 → 더워요 (deopda → deowoyo - hot)</div>
              <div class="compact-item">춥다 → 추워요 (chupda → chuwoyo - cold)</div>
              <div class="compact-item">비가 와요 (biga wayo - it's raining)</div>
              <div class="compact-item">눈이 와요 (nuni wayo - it's snowing)</div>
              <div class="compact-item">바람이 불어요 (barami bureoyo - it's windy)</div>
              <div class="compact-item">맑아요 (malgayo - it's clear)</div>
              <div class="compact-item">흐려요 (heuryeoyo - it's cloudy)</div>
              <div class="compact-item">습해요 (seuphaeyo - it's humid)</div>
              <div class="compact-item">건조해요 (geonjohaeyo - it's dry)</div>
              <div class="compact-item">따뜻해요 (ttatteuthaeyo - it's warm)</div>
              <div class="compact-item">시원해요 (siwonhaeyo - it's cool)</div>
            </div>
          </div>
          <div class="compact-row">
            <strong>Traditional Items:</strong>
            <div class="compact-content">
              <div class="compact-item">한복 (hanbok - traditional clothing)</div>
              <div class="compact-item">치마 (chima - skirt)</div>
              <div class="compact-item">저고리 (jeogori - top/jacket)</div>
              <div class="compact-item">한옥 (hanok - traditional house)</div>
              <div class="compact-item">온돌 (ondol - underfloor heating)</div>
              <div class="compact-item">한글 (hangeul - Korean alphabet)</div>
              <div class="compact-item">윷놀이 (yunnori - traditional game)</div>
              <div class="compact-item">제기차기 (jegi chagi - traditional kicking game)</div>
            </div>
          </div>
        </div>
      </div>

      <div class="reference-card verbs-card">
        <h3>Korean Verb Conjugation Table (해요체)</h3>
        <div class="reference-content">
          <details>
            <summary>Click to expand verb table (100+ verbs)</summary>
            <div style="overflow-x:auto;">
              <table class="verbs-table">
                <thead>
                  <tr>
                    <th>Verb (dict.)</th>
                    <th>English meaning</th>
                    <th>Present</th>
                    <th>Past</th>
                    <th>Future</th>
                  </tr>
                </thead>
                <tbody>
                  <!-- Generated from blog_posts/verbs_tenses.tsv (simple -다 verbs only; edit TSV, then run: python tools_update_verb_table.py) -->
                  <tr>
                    <td class="ko-cell"><div class="ko">가깝다</div><div class="rom">gakkapda</div></td>
                    <td>to be close/near</td>
                    <td class="ko-cell"><div class="ko">가까워요</div><div class="rom">gakkawoyo</div></td>
                    <td class="ko-cell"><div class="ko">가까웠어요</div><div class="rom">gakkawosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">가까울 거예요</div><div class="rom">gakkaul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">가다</div><div class="rom">gada</div></td>
                    <td>go</td>
                    <td class="ko-cell"><div class="ko">가요</div><div class="rom">gayo</div></td>
                    <td class="ko-cell"><div class="ko">갔어요</div><div class="rom">gasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">갈 거예요</div><div class="rom">gal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">가르치다</div><div class="rom">gareuchida</div></td>
                    <td>to teach / to tell (someone)</td>
                    <td class="ko-cell"><div class="ko">가르쳐요</div><div class="rom">gareuchyeoyo</div></td>
                    <td class="ko-cell"><div class="ko">가르쳤어요</div><div class="rom">gareuchyeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">가르칠 거예요</div><div class="rom">gareuchil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">가져오다</div><div class="rom">gajyeooda</div></td>
                    <td>to bring</td>
                    <td class="ko-cell"><div class="ko">가져와요</div><div class="rom">gajyeowayo</div></td>
                    <td class="ko-cell"><div class="ko">가져왔어요</div><div class="rom">gajyeowasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">가져올 거예요</div><div class="rom">gajyeool geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">갈아타다</div><div class="rom">garatada</div></td>
                    <td>to transfer</td>
                    <td class="ko-cell"><div class="ko">갈아타요</div><div class="rom">garatayo</div></td>
                    <td class="ko-cell"><div class="ko">갈아탔어요</div><div class="rom">garatasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">갈아탈 거예요</div><div class="rom">garatal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">걱정하다</div><div class="rom">geokjeonghada</div></td>
                    <td>to worry</td>
                    <td class="ko-cell"><div class="ko">걱정해요</div><div class="rom">geokjeonghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">걱정했어요</div><div class="rom">geokjeonghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">걱정할 거예요</div><div class="rom">geokjeonghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">건너다</div><div class="rom">geonneoda</div></td>
                    <td>to cross</td>
                    <td class="ko-cell"><div class="ko">건너요</div><div class="rom">geonneoyo</div></td>
                    <td class="ko-cell"><div class="ko">건넜어요</div><div class="rom">geonneosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">건널 거예요</div><div class="rom">geonneol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">걷다</div><div class="rom">geotda</div></td>
                    <td>to walk</td>
                    <td class="ko-cell"><div class="ko">걸어요</div><div class="rom">georeoyo</div></td>
                    <td class="ko-cell"><div class="ko">걸었어요</div><div class="rom">georeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">걸을 거예요</div><div class="rom">georeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">걸어가다</div><div class="rom">georeogada</div></td>
                    <td>to go by walking</td>
                    <td class="ko-cell"><div class="ko">걸어가요</div><div class="rom">georeogayo</div></td>
                    <td class="ko-cell"><div class="ko">걸어갔어요</div><div class="rom">georeogasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">걸어갈 거예요</div><div class="rom">georeogal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">걸어오다</div><div class="rom">georeooda</div></td>
                    <td>to come by walking</td>
                    <td class="ko-cell"><div class="ko">걸어와요</div><div class="rom">georeowayo</div></td>
                    <td class="ko-cell"><div class="ko">걸어왔어요</div><div class="rom">georeowasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">걸어올 거예요</div><div class="rom">georeool geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">공부하다</div><div class="rom">gongbuhada</div></td>
                    <td>to study</td>
                    <td class="ko-cell"><div class="ko">공부해요</div><div class="rom">gongbuhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">공부했어요</div><div class="rom">gongbuhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">공부할 거예요</div><div class="rom">gongbuhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">괜찮다</div><div class="rom">gwaenchanda</div></td>
                    <td>to be okay</td>
                    <td class="ko-cell"><div class="ko">괜찮아요</div><div class="rom">gwaenchanayo</div></td>
                    <td class="ko-cell"><div class="ko">괜찮았어요</div><div class="rom">gwaenchanasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">괜찮을 거예요</div><div class="rom">gwaenchaneul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">구경하다</div><div class="rom">gugyeonghada</div></td>
                    <td>to see/sightsee</td>
                    <td class="ko-cell"><div class="ko">구경해요</div><div class="rom">gugyeonghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">구경했어요</div><div class="rom">gugyeonghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">구경할 거예요</div><div class="rom">gugyeonghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">귀엽다</div><div class="rom">gwiyeopda</div></td>
                    <td>to be cute</td>
                    <td class="ko-cell"><div class="ko">귀여워요</div><div class="rom">gwiyeowoyo</div></td>
                    <td class="ko-cell"><div class="ko">귀여웠어요</div><div class="rom">gwiyeowosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">귀여울 거예요</div><div class="rom">gwiyeoul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">그렇다</div><div class="rom">geureotda</div></td>
                    <td>to be so</td>
                    <td class="ko-cell"><div class="ko">그래요</div><div class="rom">geuraeyo</div></td>
                    <td class="ko-cell"><div class="ko">그랬어요</div><div class="rom">geuraesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">그렇을 거예요</div><div class="rom">geureoheul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">그리다</div><div class="rom">geurida</div></td>
                    <td>to draw</td>
                    <td class="ko-cell"><div class="ko">그려요</div><div class="rom">geuryeoyo</div></td>
                    <td class="ko-cell"><div class="ko">그렸어요</div><div class="rom">geuryeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">그릴 거예요</div><div class="rom">geuril geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">기다리다</div><div class="rom">gidarida</div></td>
                    <td>to wait</td>
                    <td class="ko-cell"><div class="ko">기다려요</div><div class="rom">gidaryeoyo</div></td>
                    <td class="ko-cell"><div class="ko">기다렸어요</div><div class="rom">gidaryeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">기다릴 거예요</div><div class="rom">gidaril geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">길다</div><div class="rom">gilda</div></td>
                    <td>to be long</td>
                    <td class="ko-cell"><div class="ko">길어요</div><div class="rom">gireoyo</div></td>
                    <td class="ko-cell"><div class="ko">길었어요</div><div class="rom">gireosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">길 거예요</div><div class="rom">gil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">깨다</div><div class="rom">kkaeda</div></td>
                    <td>To break, shatter</td>
                    <td class="ko-cell"><div class="ko">깨요</div><div class="rom">kkaeyo</div></td>
                    <td class="ko-cell"><div class="ko">깼어요</div><div class="rom">kkaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">깰 거예요</div><div class="rom">kkael geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">나가다</div><div class="rom">nagada</div></td>
                    <td>to go out</td>
                    <td class="ko-cell"><div class="ko">나가요</div><div class="rom">nagayo</div></td>
                    <td class="ko-cell"><div class="ko">나갔어요</div><div class="rom">nagasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">나갈 거예요</div><div class="rom">nagal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">나오다</div><div class="rom">naoda</div></td>
                    <td>to come out</td>
                    <td class="ko-cell"><div class="ko">나와요</div><div class="rom">nawayo</div></td>
                    <td class="ko-cell"><div class="ko">나왔어요</div><div class="rom">nawasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">나올 거예요</div><div class="rom">naol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">날씬하다</div><div class="rom">nalssinhada</div></td>
                    <td>to be slim</td>
                    <td class="ko-cell"><div class="ko">날씬해요</div><div class="rom">nalssinhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">날씬했어요</div><div class="rom">nalssinhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">날씬할 거예요</div><div class="rom">nalssinhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">내려가다</div><div class="rom">naeryeogada</div></td>
                    <td>to go down</td>
                    <td class="ko-cell"><div class="ko">내려가요</div><div class="rom">naeryeogayo</div></td>
                    <td class="ko-cell"><div class="ko">내려갔어요</div><div class="rom">naeryeogasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">내려갈 거예요</div><div class="rom">naeryeogal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">내려오다</div><div class="rom">naeryeooda</div></td>
                    <td>to come down</td>
                    <td class="ko-cell"><div class="ko">내려와요</div><div class="rom">naeryeowayo</div></td>
                    <td class="ko-cell"><div class="ko">내려왔어요</div><div class="rom">naeryeowasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">내려올 거예요</div><div class="rom">naeryeool geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">내리다</div><div class="rom">naerida</div></td>
                    <td>to get off</td>
                    <td class="ko-cell"><div class="ko">내려요</div><div class="rom">naeryeoyo</div></td>
                    <td class="ko-cell"><div class="ko">내렸어요</div><div class="rom">naeryeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">내릴 거예요</div><div class="rom">naeril geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">놀다</div><div class="rom">nolda</div></td>
                    <td>to play</td>
                    <td class="ko-cell"><div class="ko">놀아요</div><div class="rom">norayo</div></td>
                    <td class="ko-cell"><div class="ko">놀았어요</div><div class="rom">norasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">놀 거예요</div><div class="rom">nol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">노래하다</div><div class="rom">noraehada</div></td>
                    <td>to sing</td>
                    <td class="ko-cell"><div class="ko">노래해요</div><div class="rom">noraehaeyo</div></td>
                    <td class="ko-cell"><div class="ko">노래했어요</div><div class="rom">noraehaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">노래할 거예요</div><div class="rom">noraehal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">늦다</div><div class="rom">neutda</div></td>
                    <td>to be late</td>
                    <td class="ko-cell"><div class="ko">늦어요</div><div class="rom">neujeoyo</div></td>
                    <td class="ko-cell"><div class="ko">늦었어요</div><div class="rom">neujeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">늦을 거예요</div><div class="rom">neujeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">닫다</div><div class="rom">datda</div></td>
                    <td>to close</td>
                    <td class="ko-cell"><div class="ko">닫아요</div><div class="rom">dadayo</div></td>
                    <td class="ko-cell"><div class="ko">닫았어요</div><div class="rom">dadasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">닫을 거예요</div><div class="rom">dadeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">달다</div><div class="rom">dalda</div></td>
                    <td>sweet</td>
                    <td class="ko-cell"><div class="ko">달아요</div><div class="rom">darayo</div></td>
                    <td class="ko-cell"><div class="ko">달았어요</div><div class="rom">darasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">달 거예요</div><div class="rom">dal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">덥다</div><div class="rom">deopda</div></td>
                    <td>hot</td>
                    <td class="ko-cell"><div class="ko">더워요</div><div class="rom">deowoyo</div></td>
                    <td class="ko-cell"><div class="ko">더웠어요</div><div class="rom">deowosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">더울 거예요</div><div class="rom">deoul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">도와주다</div><div class="rom">dowajuda</div></td>
                    <td>to help (someone)</td>
                    <td class="ko-cell"><div class="ko">도와줘요</div><div class="rom">dowajwoyo</div></td>
                    <td class="ko-cell"><div class="ko">도와줬어요</div><div class="rom">dowajwosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">도와줄 거예요</div><div class="rom">dowajul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">듣다</div><div class="rom">deutda</div></td>
                    <td>to listen</td>
                    <td class="ko-cell"><div class="ko">들어요</div><div class="rom">deureoyo</div></td>
                    <td class="ko-cell"><div class="ko">들었어요</div><div class="rom">deureosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">들을 거예요</div><div class="rom">deureul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">들어가다</div><div class="rom">deureogada</div></td>
                    <td>to go in / enter</td>
                    <td class="ko-cell"><div class="ko">들어가요</div><div class="rom">deureogayo</div></td>
                    <td class="ko-cell"><div class="ko">들어갔어요</div><div class="rom">deureogasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">들어갈 거예요</div><div class="rom">deureogal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">들어오다</div><div class="rom">deureooda</div></td>
                    <td>to come in / enter</td>
                    <td class="ko-cell"><div class="ko">들어와요</div><div class="rom">deureowayo</div></td>
                    <td class="ko-cell"><div class="ko">들어왔어요</div><div class="rom">deureowasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">들어올 거예요</div><div class="rom">deureool geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">따뜻하다</div><div class="rom">ttatteuthada</div></td>
                    <td>warm</td>
                    <td class="ko-cell"><div class="ko">따뜻해요</div><div class="rom">ttatteuthaeyo</div></td>
                    <td class="ko-cell"><div class="ko">따뜻했어요</div><div class="rom">ttatteuthaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">따뜻할 거예요</div><div class="rom">ttatteuthal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">뚱뚱하다</div><div class="rom">ttungttunghada</div></td>
                    <td>to be fat</td>
                    <td class="ko-cell"><div class="ko">뚱뚱해요</div><div class="rom">ttungttunghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">뚱뚱했어요</div><div class="rom">ttungttunghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">뚱뚱할 거예요</div><div class="rom">ttungttunghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">마르다</div><div class="rom">mareuda</div></td>
                    <td>to be skinny / thin</td>
                    <td class="ko-cell"><div class="ko">말라요</div><div class="rom">malrayo</div></td>
                    <td class="ko-cell"><div class="ko">말랐어요</div><div class="rom">malrasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">마를 거예요</div><div class="rom">mareul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">마시다</div><div class="rom">masida</div></td>
                    <td>to drink</td>
                    <td class="ko-cell"><div class="ko">마셔요</div><div class="rom">masyeoyo</div></td>
                    <td class="ko-cell"><div class="ko">마셨어요</div><div class="rom">masyeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">마실 거예요</div><div class="rom">masil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">만나다</div><div class="rom">mannada</div></td>
                    <td>to meet</td>
                    <td class="ko-cell"><div class="ko">만나요</div><div class="rom">mannayo</div></td>
                    <td class="ko-cell"><div class="ko">만났어요</div><div class="rom">mannasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">만날 거예요</div><div class="rom">mannal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">만들다</div><div class="rom">mandeulda</div></td>
                    <td>to make</td>
                    <td class="ko-cell"><div class="ko">만들어요</div><div class="rom">mandeureoyo</div></td>
                    <td class="ko-cell"><div class="ko">만들었어요</div><div class="rom">mandeureosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">만들 거예요</div><div class="rom">mandeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">많다</div><div class="rom">manda</div></td>
                    <td>to be many/much (only ㄴ pronounced)</td>
                    <td class="ko-cell"><div class="ko">많아요</div><div class="rom">manayo</div></td>
                    <td class="ko-cell"><div class="ko">많았어요</div><div class="rom">manasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">많을 거예요</div><div class="rom">maneul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">말하다</div><div class="rom">malhada</div></td>
                    <td>to speak</td>
                    <td class="ko-cell"><div class="ko">말해요</div><div class="rom">malhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">말했어요</div><div class="rom">malhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">말할 거예요</div><div class="rom">malhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">맑다</div><div class="rom">makda</div></td>
                    <td>clear</td>
                    <td class="ko-cell"><div class="ko">맑아요</div><div class="rom">magayo</div></td>
                    <td class="ko-cell"><div class="ko">맑았어요</div><div class="rom">magasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">맑을 거예요</div><div class="rom">mageul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">맛없다</div><div class="rom">maseotda</div></td>
                    <td>not tasty</td>
                    <td class="ko-cell"><div class="ko">맛없어요</div><div class="rom">maseobeoyo</div></td>
                    <td class="ko-cell"><div class="ko">맛없었어요</div><div class="rom">maseobeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">맛없을 거예요</div><div class="rom">maseobeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">맛있다</div><div class="rom">masitda</div></td>
                    <td>tasty</td>
                    <td class="ko-cell"><div class="ko">맛있어요</div><div class="rom">masisseoyo</div></td>
                    <td class="ko-cell"><div class="ko">맛있었어요</div><div class="rom">masisseosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">맛있을 거예요</div><div class="rom">masisseul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">맞다</div><div class="rom">matda</div></td>
                    <td>to be right / correct</td>
                    <td class="ko-cell"><div class="ko">맞아요</div><div class="rom">majayo</div></td>
                    <td class="ko-cell"><div class="ko">맞았어요</div><div class="rom">majasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">맞을 거예요</div><div class="rom">majeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">맵다</div><div class="rom">maepda</div></td>
                    <td>spicy</td>
                    <td class="ko-cell"><div class="ko">매워요</div><div class="rom">maewoyo</div></td>
                    <td class="ko-cell"><div class="ko">매웠어요</div><div class="rom">maewosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">매울 거예요</div><div class="rom">maeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">먹다</div><div class="rom">meokda</div></td>
                    <td>eat</td>
                    <td class="ko-cell"><div class="ko">먹어요</div><div class="rom">meogeoyo</div></td>
                    <td class="ko-cell"><div class="ko">먹었어요</div><div class="rom">meogeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">먹을 거예요</div><div class="rom">meogeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">멋있다</div><div class="rom">meositda</div></td>
                    <td>to be stylish / cool</td>
                    <td class="ko-cell"><div class="ko">멋있어요</div><div class="rom">meosisseoyo</div></td>
                    <td class="ko-cell"><div class="ko">멋있었어요</div><div class="rom">meosisseosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">멋있을 거예요</div><div class="rom">meosisseul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">모르다</div><div class="rom">moreuda</div></td>
                    <td>to not know</td>
                    <td class="ko-cell"><div class="ko">몰라요</div><div class="rom">molrayo</div></td>
                    <td class="ko-cell"><div class="ko">몰랐어요</div><div class="rom">molrasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">모를 거예요</div><div class="rom">moreul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">물어보다</div><div class="rom">mureoboda</div></td>
                    <td>to ask</td>
                    <td class="ko-cell"><div class="ko">물어봐요</div><div class="rom">mureobwayo</div></td>
                    <td class="ko-cell"><div class="ko">물어봤어요</div><div class="rom">mureobwasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">물어볼 거예요</div><div class="rom">mureobol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">바쁘다</div><div class="rom">bappeuda</div></td>
                    <td>to be busy</td>
                    <td class="ko-cell"><div class="ko">바빠요</div><div class="rom">bappayo</div></td>
                    <td class="ko-cell"><div class="ko">바빴어요</div><div class="rom">bappasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">바쁠 거예요</div><div class="rom">bappeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">배우다</div><div class="rom">baeuda</div></td>
                    <td>to learn</td>
                    <td class="ko-cell"><div class="ko">배워요</div><div class="rom">baewoyo</div></td>
                    <td class="ko-cell"><div class="ko">배웠어요</div><div class="rom">baewosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">배울 거예요</div><div class="rom">baeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">버리다</div><div class="rom">beorida</div></td>
                    <td>to throw away</td>
                    <td class="ko-cell"><div class="ko">버려요</div><div class="rom">beoryeoyo</div></td>
                    <td class="ko-cell"><div class="ko">버렸어요</div><div class="rom">beoryeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">버릴 거예요</div><div class="rom">beoril geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">벗다</div><div class="rom">beotda</div></td>
                    <td>to take off (clothes)</td>
                    <td class="ko-cell"><div class="ko">벗어요</div><div class="rom">beoseoyo</div></td>
                    <td class="ko-cell"><div class="ko">벗었어요</div><div class="rom">beoseosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">벗을 거예요</div><div class="rom">beoseul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">보내다</div><div class="rom">bonaeda</div></td>
                    <td>to spend (time)</td>
                    <td class="ko-cell"><div class="ko">보내요</div><div class="rom">bonaeyo</div></td>
                    <td class="ko-cell"><div class="ko">보냈어요</div><div class="rom">bonaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">보낼 거예요</div><div class="rom">bonael geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">보다</div><div class="rom">boda</div></td>
                    <td>see/watch</td>
                    <td class="ko-cell"><div class="ko">봐요</div><div class="rom">bwayo</div></td>
                    <td class="ko-cell"><div class="ko">봤어요</div><div class="rom">bwasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">볼 거예요</div><div class="rom">bol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">보이다</div><div class="rom">boida</div></td>
                    <td>to be visible / to see</td>
                    <td class="ko-cell"><div class="ko">보여요</div><div class="rom">boyeoyo</div></td>
                    <td class="ko-cell"><div class="ko">보였어요</div><div class="rom">boyeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">보일 거예요</div><div class="rom">boil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">비싸다</div><div class="rom">bissada</div></td>
                    <td>to be expensive</td>
                    <td class="ko-cell"><div class="ko">비싸요</div><div class="rom">bissayo</div></td>
                    <td class="ko-cell"><div class="ko">비쌌어요</div><div class="rom">bissasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">비쌀 거예요</div><div class="rom">bissal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">빌리다</div><div class="rom">bilrida</div></td>
                    <td>to borrow</td>
                    <td class="ko-cell"><div class="ko">빌려요</div><div class="rom">bilryeoyo</div></td>
                    <td class="ko-cell"><div class="ko">빌렸어요</div><div class="rom">bilryeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">빌릴 거예요</div><div class="rom">bilril geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">사다</div><div class="rom">sada</div></td>
                    <td>to buy</td>
                    <td class="ko-cell"><div class="ko">사요</div><div class="rom">sayo</div></td>
                    <td class="ko-cell"><div class="ko">샀어요</div><div class="rom">sasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">살 거예요</div><div class="rom">sal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">사랑하다</div><div class="rom">saranghada</div></td>
                    <td>to love</td>
                    <td class="ko-cell"><div class="ko">사랑해요</div><div class="rom">saranghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">사랑했어요</div><div class="rom">saranghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">사랑할 거예요</div><div class="rom">saranghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">산책하다</div><div class="rom">sanchaekhada</div></td>
                    <td>to take a walk</td>
                    <td class="ko-cell"><div class="ko">산책해요</div><div class="rom">sanchaekhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">산책했어요</div><div class="rom">sanchaekhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">산책할 거예요</div><div class="rom">sanchaekhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">살다</div><div class="rom">salda</div></td>
                    <td>to live</td>
                    <td class="ko-cell"><div class="ko">살아요</div><div class="rom">sarayo</div></td>
                    <td class="ko-cell"><div class="ko">살았어요</div><div class="rom">sarasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">살 거예요</div><div class="rom">sal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">새다</div><div class="rom">saeda</div></td>
                    <td>To leak</td>
                    <td class="ko-cell"><div class="ko">새요</div><div class="rom">saeyo</div></td>
                    <td class="ko-cell"><div class="ko">샜어요</div><div class="rom">saesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">샐 거예요</div><div class="rom">sael geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">서다</div><div class="rom">seoda</div></td>
                    <td>to stand</td>
                    <td class="ko-cell"><div class="ko">서요</div><div class="rom">seoyo</div></td>
                    <td class="ko-cell"><div class="ko">섰어요</div><div class="rom">seosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">설 거예요</div><div class="rom">seol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">소개하다</div><div class="rom">sogaehada</div></td>
                    <td>to introduce</td>
                    <td class="ko-cell"><div class="ko">소개해요</div><div class="rom">sogaehaeyo</div></td>
                    <td class="ko-cell"><div class="ko">소개했어요</div><div class="rom">sogaehaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">소개할 거예요</div><div class="rom">sogaehal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">쇼핑하다</div><div class="rom">syopinghada</div></td>
                    <td>to go shopping</td>
                    <td class="ko-cell"><div class="ko">쇼핑해요</div><div class="rom">syopinghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">쇼핑했어요</div><div class="rom">syopinghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">쇼핑할 거예요</div><div class="rom">syopinghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">수영하다</div><div class="rom">suyeonghada</div></td>
                    <td>to swim</td>
                    <td class="ko-cell"><div class="ko">수영해요</div><div class="rom">suyeonghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">수영했어요</div><div class="rom">suyeonghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">수영할 거예요</div><div class="rom">suyeonghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">쉬다</div><div class="rom">swida</div></td>
                    <td>to rest</td>
                    <td class="ko-cell"><div class="ko">쉬어요</div><div class="rom">swieoyo</div></td>
                    <td class="ko-cell"><div class="ko">쉬었어요</div><div class="rom">swieosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">쉴 거예요</div><div class="rom">swil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">습하다</div><div class="rom">seuphada</div></td>
                    <td>humid</td>
                    <td class="ko-cell"><div class="ko">습해요</div><div class="rom">seuphaeyo</div></td>
                    <td class="ko-cell"><div class="ko">습했어요</div><div class="rom">seuphaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">습할 거예요</div><div class="rom">seuphal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">시다</div><div class="rom">sida</div></td>
                    <td>sour</td>
                    <td class="ko-cell"><div class="ko">셔요</div><div class="rom">syeoyo</div></td>
                    <td class="ko-cell"><div class="ko">셨어요</div><div class="rom">syeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">실 거예요</div><div class="rom">sil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">시원하다</div><div class="rom">siwonhada</div></td>
                    <td>cool</td>
                    <td class="ko-cell"><div class="ko">시원해요</div><div class="rom">siwonhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">시원했어요</div><div class="rom">siwonhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">시원할 거예요</div><div class="rom">siwonhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">싱겁다</div><div class="rom">singgeopda</div></td>
                    <td>bland</td>
                    <td class="ko-cell"><div class="ko">싱거워요</div><div class="rom">singgeowoyo</div></td>
                    <td class="ko-cell"><div class="ko">싱거웠어요</div><div class="rom">singgeowosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">싱거울 거예요</div><div class="rom">singgeoul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">싸다</div><div class="rom">ssada</div></td>
                    <td>to be cheap</td>
                    <td class="ko-cell"><div class="ko">싸요</div><div class="rom">ssayo</div></td>
                    <td class="ko-cell"><div class="ko">쌌어요</div><div class="rom">ssasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">쌀 거예요</div><div class="rom">ssal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">쓰다</div><div class="rom">sseuda</div></td>
                    <td>to write</td>
                    <td class="ko-cell"><div class="ko">써요</div><div class="rom">sseoyo</div></td>
                    <td class="ko-cell"><div class="ko">썼어요</div><div class="rom">sseosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">쓸 거예요</div><div class="rom">sseul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">아프다</div><div class="rom">apeuda</div></td>
                    <td>to be sick</td>
                    <td class="ko-cell"><div class="ko">아파요</div><div class="rom">apayo</div></td>
                    <td class="ko-cell"><div class="ko">아팠어요</div><div class="rom">apasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">아플 거예요</div><div class="rom">apeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">앉다</div><div class="rom">anda</div></td>
                    <td>to sit</td>
                    <td class="ko-cell"><div class="ko">앉아요</div><div class="rom">anayo</div></td>
                    <td class="ko-cell"><div class="ko">앉았어요</div><div class="rom">anasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">앉을 거예요</div><div class="rom">aneul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">알다</div><div class="rom">alda</div></td>
                    <td>to know</td>
                    <td class="ko-cell"><div class="ko">알아요</div><div class="rom">arayo</div></td>
                    <td class="ko-cell"><div class="ko">알았어요</div><div class="rom">arasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">알 거예요</div><div class="rom">al geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">연락하다</div><div class="rom">yeonrakhada</div></td>
                    <td>to contact</td>
                    <td class="ko-cell"><div class="ko">연락해요</div><div class="rom">yeonrakhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">연락했어요</div><div class="rom">yeonrakhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">연락할 거예요</div><div class="rom">yeonrakhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">열다</div><div class="rom">yeolda</div></td>
                    <td>to open</td>
                    <td class="ko-cell"><div class="ko">열어요</div><div class="rom">yeoreoyo</div></td>
                    <td class="ko-cell"><div class="ko">열었어요</div><div class="rom">yeoreosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">열 거예요</div><div class="rom">yeol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">여행하다</div><div class="rom">yeohaenghada</div></td>
                    <td>to travel</td>
                    <td class="ko-cell"><div class="ko">여행해요</div><div class="rom">yeohaenghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">여행했어요</div><div class="rom">yeohaenghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">여행할 거예요</div><div class="rom">yeohaenghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">예쁘다</div><div class="rom">yeppeuda</div></td>
                    <td>to be pretty</td>
                    <td class="ko-cell"><div class="ko">예뻐요</div><div class="rom">yeppeoyo</div></td>
                    <td class="ko-cell"><div class="ko">예뻤어요</div><div class="rom">yeppeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">예쁠 거예요</div><div class="rom">yeppeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">오다</div><div class="rom">oda</div></td>
                    <td>come</td>
                    <td class="ko-cell"><div class="ko">와요</div><div class="rom">wayo</div></td>
                    <td class="ko-cell"><div class="ko">왔어요</div><div class="rom">wasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">올 거예요</div><div class="rom">ol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">올라가다</div><div class="rom">olragada</div></td>
                    <td>to go up</td>
                    <td class="ko-cell"><div class="ko">올라가요</div><div class="rom">olragayo</div></td>
                    <td class="ko-cell"><div class="ko">올라갔어요</div><div class="rom">olragasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">올라갈 거예요</div><div class="rom">olragal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">올라오다</div><div class="rom">olraoda</div></td>
                    <td>to come up</td>
                    <td class="ko-cell"><div class="ko">올라와요</div><div class="rom">olrawayo</div></td>
                    <td class="ko-cell"><div class="ko">올라왔어요</div><div class="rom">olrawasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">올라올 거예요</div><div class="rom">olraol geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">요리하다</div><div class="rom">yorihada</div></td>
                    <td>to cook</td>
                    <td class="ko-cell"><div class="ko">요리해요</div><div class="rom">yorihaeyo</div></td>
                    <td class="ko-cell"><div class="ko">요리했어요</div><div class="rom">yorihaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">요리할 거예요</div><div class="rom">yorihal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">운동하다</div><div class="rom">undonghada</div></td>
                    <td>to exercise</td>
                    <td class="ko-cell"><div class="ko">운동해요</div><div class="rom">undonghaeyo</div></td>
                    <td class="ko-cell"><div class="ko">운동했어요</div><div class="rom">undonghaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">운동할 거예요</div><div class="rom">undonghal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">운전하다</div><div class="rom">unjeonhada</div></td>
                    <td>to drive</td>
                    <td class="ko-cell"><div class="ko">운전해요</div><div class="rom">unjeonhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">운전했어요</div><div class="rom">unjeonhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">운전할 거예요</div><div class="rom">unjeonhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">읊다</div><div class="rom">eulda</div></td>
                    <td>to recite/chant (only ㅍ pronounced)</td>
                    <td class="ko-cell"><div class="ko">읊어요</div><div class="rom">eupeoyo</div></td>
                    <td class="ko-cell"><div class="ko">읊었어요</div><div class="rom">eupeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">읊을 거예요</div><div class="rom">eupeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">이사하다</div><div class="rom">isahada</div></td>
                    <td>to move (houses)</td>
                    <td class="ko-cell"><div class="ko">이사해요</div><div class="rom">isahaeyo</div></td>
                    <td class="ko-cell"><div class="ko">이사했어요</div><div class="rom">isahaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">이사할 거예요</div><div class="rom">isahal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">이야기하다</div><div class="rom">iyagihada</div></td>
                    <td>to talk</td>
                    <td class="ko-cell"><div class="ko">이야기해요</div><div class="rom">iyagihaeyo</div></td>
                    <td class="ko-cell"><div class="ko">이야기했어요</div><div class="rom">iyagihaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">이야기할 거예요</div><div class="rom">iyagihal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">일어나다</div><div class="rom">ireonada</div></td>
                    <td>to wake up</td>
                    <td class="ko-cell"><div class="ko">일어나요</div><div class="rom">ireonayo</div></td>
                    <td class="ko-cell"><div class="ko">일어났어요</div><div class="rom">ireonasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">일어날 거예요</div><div class="rom">ireonal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">일하다</div><div class="rom">ilhada</div></td>
                    <td>to work</td>
                    <td class="ko-cell"><div class="ko">일해요</div><div class="rom">ilhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">일했어요</div><div class="rom">ilhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">일할 거예요</div><div class="rom">ilhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">읽다</div><div class="rom">ikda</div></td>
                    <td>to read (only ㄱ pronounced)</td>
                    <td class="ko-cell"><div class="ko">읽어요</div><div class="rom">igeoyo</div></td>
                    <td class="ko-cell"><div class="ko">읽었어요</div><div class="rom">igeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">읽을 거예요</div><div class="rom">igeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">입다</div><div class="rom">ipda</div></td>
                    <td>to wear</td>
                    <td class="ko-cell"><div class="ko">입어요</div><div class="rom">ibeoyo</div></td>
                    <td class="ko-cell"><div class="ko">입었어요</div><div class="rom">ibeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">입을 거예요</div><div class="rom">ibeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">자다</div><div class="rom">jada</div></td>
                    <td>to sleep</td>
                    <td class="ko-cell"><div class="ko">자요</div><div class="rom">jayo</div></td>
                    <td class="ko-cell"><div class="ko">잤어요</div><div class="rom">jasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">잘 거예요</div><div class="rom">jal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">작다</div><div class="rom">jakda</div></td>
                    <td>to be small</td>
                    <td class="ko-cell"><div class="ko">작아요</div><div class="rom">jagayo</div></td>
                    <td class="ko-cell"><div class="ko">작았어요</div><div class="rom">jagasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">작을 거예요</div><div class="rom">jageul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">잘생기다</div><div class="rom">jalsaenggida</div></td>
                    <td>to be handsome</td>
                    <td class="ko-cell"><div class="ko">잘생겨요</div><div class="rom">jalsaenggyeoyo</div></td>
                    <td class="ko-cell"><div class="ko">잘생겼어요</div><div class="rom">jalsaenggyeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">잘생길 거예요</div><div class="rom">jalsaenggil geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">재미없다</div><div class="rom">jaemieotda</div></td>
                    <td>not fun, boring</td>
                    <td class="ko-cell"><div class="ko">재미없어요</div><div class="rom">jaemieobeoyo</div></td>
                    <td class="ko-cell"><div class="ko">재미없었어요</div><div class="rom">jaemieobeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">재미없을 거예요</div><div class="rom">jaemieobeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">재미있다</div><div class="rom">jaemiitda</div></td>
                    <td>fun, interesting</td>
                    <td class="ko-cell"><div class="ko">재미있어요</div><div class="rom">jaemiisseoyo</div></td>
                    <td class="ko-cell"><div class="ko">재미있었어요</div><div class="rom">jaemiisseosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">재미있을 거예요</div><div class="rom">jaemiisseul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">전화하다</div><div class="rom">jeonhwahada</div></td>
                    <td>to call</td>
                    <td class="ko-cell"><div class="ko">전화해요</div><div class="rom">jeonhwahaeyo</div></td>
                    <td class="ko-cell"><div class="ko">전화했어요</div><div class="rom">jeonhwahaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">전화할 거예요</div><div class="rom">jeonhwahal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">좋다</div><div class="rom">jotda</div></td>
                    <td>[조따] (jo-tta) = to be good</td>
                    <td class="ko-cell"><div class="ko">좋아요</div><div class="rom">johayo</div></td>
                    <td class="ko-cell"><div class="ko">좋았어요</div><div class="rom">johasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">좋을 거예요</div><div class="rom">joheul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">좋아하다</div><div class="rom">johahada</div></td>
                    <td>to like</td>
                    <td class="ko-cell"><div class="ko">좋아해요</div><div class="rom">johahaeyo</div></td>
                    <td class="ko-cell"><div class="ko">좋아했어요</div><div class="rom">johahaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">좋아할 거예요</div><div class="rom">johahal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">주다</div><div class="rom">juda</div></td>
                    <td>to give</td>
                    <td class="ko-cell"><div class="ko">줘요</div><div class="rom">jwoyo</div></td>
                    <td class="ko-cell"><div class="ko">줬어요</div><div class="rom">jwosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">줄 거예요</div><div class="rom">jul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">즐겁다</div><div class="rom">jeulgeopda</div></td>
                    <td>to be pleased, enjoyable</td>
                    <td class="ko-cell"><div class="ko">즐거워요</div><div class="rom">jeulgeowoyo</div></td>
                    <td class="ko-cell"><div class="ko">즐거웠어요</div><div class="rom">jeulgeowosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">즐거울 거예요</div><div class="rom">jeulgeoul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">지나다</div><div class="rom">jinada</div></td>
                    <td>to pass</td>
                    <td class="ko-cell"><div class="ko">지나요</div><div class="rom">jinayo</div></td>
                    <td class="ko-cell"><div class="ko">지났어요</div><div class="rom">jinasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">지날 거예요</div><div class="rom">jinal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">짜다</div><div class="rom">jjada</div></td>
                    <td>salty</td>
                    <td class="ko-cell"><div class="ko">짜요</div><div class="rom">jjayo</div></td>
                    <td class="ko-cell"><div class="ko">짰어요</div><div class="rom">jjasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">짤 거예요</div><div class="rom">jjal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">짧다</div><div class="rom">jjalda</div></td>
                    <td>to be short</td>
                    <td class="ko-cell"><div class="ko">짧아요</div><div class="rom">jjabayo</div></td>
                    <td class="ko-cell"><div class="ko">짧았어요</div><div class="rom">jjabasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">짧을 거예요</div><div class="rom">jjabeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">쬐다</div><div class="rom">jjoeda</div></td>
                    <td>To sunbathe, expose to sunlight</td>
                    <td class="ko-cell"><div class="ko">쬐요</div><div class="rom">jjoeyo</div></td>
                    <td class="ko-cell"><div class="ko">쬤어요</div><div class="rom">jjoesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">쬘 거예요</div><div class="rom">jjoel geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">찾다</div><div class="rom">chatda</div></td>
                    <td>to look for</td>
                    <td class="ko-cell"><div class="ko">찾아요</div><div class="rom">chajayo</div></td>
                    <td class="ko-cell"><div class="ko">찾았어요</div><div class="rom">chajasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">찾을 거예요</div><div class="rom">chajeul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">첨부하다</div><div class="rom">cheopbuhada</div></td>
                    <td>to attach</td>
                    <td class="ko-cell"><div class="ko">첨부해요</div><div class="rom">cheopbuhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">첨부했어요</div><div class="rom">cheopbuhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">첨부할 거예요</div><div class="rom">cheopbuhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">청소하다</div><div class="rom">cheongsohada</div></td>
                    <td>to clean</td>
                    <td class="ko-cell"><div class="ko">청소해요</div><div class="rom">cheongsohaeyo</div></td>
                    <td class="ko-cell"><div class="ko">청소했어요</div><div class="rom">cheongsohaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">청소할 거예요</div><div class="rom">cheongsohal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">축하하다</div><div class="rom">chukhahada</div></td>
                    <td>to congratulate</td>
                    <td class="ko-cell"><div class="ko">축하해요</div><div class="rom">chukhahaeyo</div></td>
                    <td class="ko-cell"><div class="ko">축하했어요</div><div class="rom">chukhahaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">축하할 거예요</div><div class="rom">chukhahal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">출근하다</div><div class="rom">chulgeunhada</div></td>
                    <td>to go to work</td>
                    <td class="ko-cell"><div class="ko">출근해요</div><div class="rom">chulgeunhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">출근했어요</div><div class="rom">chulgeunhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">출근할 거예요</div><div class="rom">chulgeunhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">춤추다</div><div class="rom">chupchuda</div></td>
                    <td>to dance</td>
                    <td class="ko-cell"><div class="ko">춤춰요</div><div class="rom">chupchwoyo</div></td>
                    <td class="ko-cell"><div class="ko">춤췄어요</div><div class="rom">chupchwosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">춤출 거예요</div><div class="rom">chupchul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">춥다</div><div class="rom">chupda</div></td>
                    <td>cold</td>
                    <td class="ko-cell"><div class="ko">추워요</div><div class="rom">chuwoyo</div></td>
                    <td class="ko-cell"><div class="ko">추웠어요</div><div class="rom">chuwosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">추울 거예요</div><div class="rom">chuul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">크다</div><div class="rom">keuda</div></td>
                    <td>to be big/large</td>
                    <td class="ko-cell"><div class="ko">커요</div><div class="rom">keoyo</div></td>
                    <td class="ko-cell"><div class="ko">컸어요</div><div class="rom">keosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">클 거예요</div><div class="rom">keul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">타다</div><div class="rom">tada</div></td>
                    <td>to get on/ride</td>
                    <td class="ko-cell"><div class="ko">타요</div><div class="rom">tayo</div></td>
                    <td class="ko-cell"><div class="ko">탔어요</div><div class="rom">tasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">탈 거예요</div><div class="rom">tal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">태다</div><div class="rom">taeda</div></td>
                    <td>To clean, wipe</td>
                    <td class="ko-cell"><div class="ko">태요</div><div class="rom">taeyo</div></td>
                    <td class="ko-cell"><div class="ko">탰어요</div><div class="rom">taesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">탤 거예요</div><div class="rom">tael geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">퇴근하다</div><div class="rom">toegeunhada</div></td>
                    <td>to leave work</td>
                    <td class="ko-cell"><div class="ko">퇴근해요</div><div class="rom">toegeunhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">퇴근했어요</div><div class="rom">toegeunhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">퇴근할 거예요</div><div class="rom">toegeunhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">팔다</div><div class="rom">palda</div></td>
                    <td>to sell</td>
                    <td class="ko-cell"><div class="ko">팔아요</div><div class="rom">parayo</div></td>
                    <td class="ko-cell"><div class="ko">팔았어요</div><div class="rom">parasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">팔 거예요</div><div class="rom">pal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">피곤하다</div><div class="rom">pigonhada</div></td>
                    <td>to be tired</td>
                    <td class="ko-cell"><div class="ko">피곤해요</div><div class="rom">pigonhaeyo</div></td>
                    <td class="ko-cell"><div class="ko">피곤했어요</div><div class="rom">pigonhaesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">피곤할 거예요</div><div class="rom">pigonhal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">하다</div><div class="rom">hada</div></td>
                    <td>to do</td>
                    <td class="ko-cell"><div class="ko">해요</div><div class="rom">haeyo</div></td>
                    <td class="ko-cell"><div class="ko">했어요</div><div class="rom">haesseoyo</div></td>
                    <td class="ko-cell"><div class="ko">할 거예요</div><div class="rom">hal geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">핥다</div><div class="rom">halda</div></td>
                    <td>to lick (only ㄹ pronounced)</td>
                    <td class="ko-cell"><div class="ko">핥아요</div><div class="rom">hatayo</div></td>
                    <td class="ko-cell"><div class="ko">핥았어요</div><div class="rom">hatasseoyo</div></td>
                    <td class="ko-cell"><div class="ko">핥을 거예요</div><div class="rom">hateul geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">흐리다</div><div class="rom">heurida</div></td>
                    <td>cloudy</td>
                    <td class="ko-cell"><div class="ko">흐려요</div><div class="rom">heuryeoyo</div></td>
                    <td class="ko-cell"><div class="ko">흐렸어요</div><div class="rom">heuryeosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">흐릴 거예요</div><div class="rom">heuril geoyeyo</div></td>
                  </tr>
                  <tr>
                    <td class="ko-cell"><div class="ko">힘들다</div><div class="rom">hipdeulda</div></td>
                    <td>to have a hard time</td>
                    <td class="ko-cell"><div class="ko">힘들어요</div><div class="rom">hipdeureoyo</div></td>
                    <td class="ko-cell"><div class="ko">힘들었어요</div><div class="rom">hipdeureosseoyo</div></td>
                    <td class="ko-cell"><div class="ko">힘들 거예요</div><div class="rom">hipdeul geoyeyo</div></td>
                  </tr>
</tbody>
              </table>
            </div>
          </details>  
        </div>
      </div>

      <div class="reference-card proverbs-card">
        <h3>Korean Proverbs</h3>
        <div class="reference-content">
          <ul class="korean-list">
            <li>꿩 대신 닭 (Kkwong daesin dak) - "Chicken instead of pheasant"
              <br><span class="proverb-meaning">Meaning: When you can't get what you want, you should be satisfied with the next best thing.
              <br>Similar to English: "A bird in the hand is worth two in the bush" or "Better than nothing"</span>
            </li>
            <li>옷이 날개다 (Osi nalgaeda) - "Clothes are wings"
              <br><span class="proverb-meaning">Meaning: Clothes give you wings - suggesting that proper attire can help you achieve your goals</span>
            </li>
            <li>그림의 떡 (Geulim-ui tteok) - "Rice cake in a picture"
              <br><span class="proverb-meaning">Meaning: Similar to "pie in the sky" - something that looks good but is unattainable</span>
            </li>
            <li>무소식이 희소식이다 (Musosigi huisosigida) - "No news is good news"
              <br><span class="proverb-meaning">Meaning: When you don't hear anything, it usually means everything is fine</span>
            </li>
            <li>천리 길도 한 걸음부터 (cheolli gildo han georeumbuteo) - "Even a thousand-mile journey begins with a single step"
              <br><span class="proverb-meaning">Meaning: Every great achievement starts with taking the first step, no matter how small</span>
            </li>
          </ul>
        </div>
      </div>
    </div>
  </div>
</div>

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  color: #6b7280;
  font-size: 0.85rem;
  font-weight: 500;
  font-family: -apple-system, BlinkMacSystemFont, 'Inter', 'Segoe UI', system-ui, sans-serif;
}

.class-summary {
  color: #4b5563;
  font-size: 0.9rem;
  line-height: 1.6;
  margin-top: 0.25rem;
  font-weight: 400;
  font-family: -apple-system, BlinkMacSystemFont, 'Inter', 'Segoe UI', system-ui, sans-serif;
}

.reference-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.reference-card {
  border-radius: 12px;
  padding: 0;
  border: 2px solid #fff;
  box-shadow: 0 4px 8px rgba(0,0,0,0.15);
  overflow: hidden;
  background: #fff;
}

.reference-card h3 {
  margin: 0;
  padding: 1rem 1.25rem;
  font-size: 1.2rem;
  font-weight: bold;
  color: #2196F3;
  text-align: center;
  border-radius: 0;
  border: none;
  background: #f8f9fa;
  border-bottom: 2px solid #e9ecef;
}

.reference-content {
  font-size: 0.85rem;
  padding: 1rem;
  background: white;
  min-height: 180px;
}

.compact-row {
  margin-bottom: 0.5rem;
  padding: 0.5rem;
  background: #f9f9f9;
  border-radius: 4px;
  border: 1px solid #ddd;
  line-height: 1.3;
}

.compact-row:last-child {
  margin-bottom: 0;
}

.compact-row strong {
  color: #333;
  font-weight: 700;
  margin-right: 0;
  display: block;
  margin-bottom: 0.4rem;
  font-size: 0.95rem;
  border-bottom: 1px solid #eee;
  padding-bottom: 0.3rem;
}

.compact-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.3rem 1.2rem;
  align-items: start;
}

.compact-item {
  display: flex;
  align-items: baseline;
  padding: 0.15rem 0;
  font-size: 0.85rem;
}

.korean-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.korean-list li {
  padding: 0.5rem 0;
  border-bottom: 1px solid #eee;
  color: #444;
  display: block;
  line-height: 1.5;
}

.korean-list li:last-child {
  border-bottom: none;
}

.korean-list li::after {
  content: none;
}

.alphabet-section, .number-section, .time-section, .vocab-section, .rules-section, .grammar-section {
  margin-bottom: 1rem;
  padding: 0;
}

.alphabet-section h4, .number-section h4, .time-section h4, .vocab-section h4, .rules-section h4, .grammar-section h4 {
  color: #555;
  margin-bottom: 0.5rem;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0;
}

.formality-section {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid #eee;
}

.proverb-meaning {
  display: block;
  font-size: 0.9em;
  color: #666;
  margin-top: 0.5rem;
  font-style: italic;
  line-height: 1.5;
}

/* Special styling for proverbs */
.reference-card.proverbs-card {
  grid-column: 1 / -1;
  width: 100%;
}

/* Make the verbs table span the full grid width (2-column layout) */
.reference-card.verbs-card {
  grid-column: 1 / -1;
  width: 100%;
}

.reference-card.verbs-card .reference-content {
  padding: 0.75rem;
  min-height: auto;
}

.reference-card.verbs-card table {
  width: 100%;
}

/* Verbs table styling */
.verbs-table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  border: 1px solid #e5e7eb;
  border-radius: 8px;
  overflow: hidden;
  background: #fff;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.verbs-table thead th {
  position: sticky;
  top: 0;
  background: #2196F3;
  border-bottom: 2px solid #1976D2;
  color: #ffffff;
  font-weight: 600;
  padding: 0.875rem 0.75rem;
  text-align: left;
  white-space: nowrap;
  font-size: 0.875rem;
  letter-spacing: 0.025em;
  text-transform: uppercase;
  z-index: 10;
}

.verbs-table thead th:first-child {
  border-top-left-radius: 8px;
}

.verbs-table thead th:last-child {
  border-top-right-radius: 8px;
}

.verbs-table tbody td {
  border-top: 1px solid #e5e7eb;
  padding: 0.75rem;
  vertical-align: top;
  transition: background-color 0.15s ease;
  font-size: 0.9rem;
}

.verbs-table tbody tr {
  transition: all 0.15s ease;
}

.verbs-table tbody tr:nth-child(even) td {
  background: #f9fafb;
}

.verbs-table tbody tr:hover td {
  background: #e3f2fd;
}

.verbs-table tbody tr:last-child td:first-child {
  border-bottom-left-radius: 8px;
}

.verbs-table tbody tr:last-child td:last-child {
  border-bottom-right-radius: 8px;
}

.verbs-table .ko {
  font-weight: 600;
  color: #1976D2;
  line-height: 1.2;
  font-size: 1rem;
  font-family: 'Segoe UI', 'Apple SD Gothic Neo', 'Noto Sans CJK KR', sans-serif;
}

.verbs-table .rom {
  margin-top: 0.25rem;
  font-size: 0.75rem;
  color: #6b7280;
  line-height: 1.1;
  font-style: italic;
  font-family: -apple-system, BlinkMacSystemFont, 'Inter', 'Segoe UI', system-ui, sans-serif;
}

.verbs-table td.ko-cell {
  min-width: 160px;
}

.verbs-table tbody td:nth-child(2) {
  color: #4b5563;
  font-weight: 500;
  font-size: 0.85rem;
}

/* Details/Summary styling for verb table */
.reference-card.verbs-card details {
  margin: 0;
}

.reference-card.verbs-card summary {
  cursor: pointer;
  padding: 0.75rem 1rem;
  background: #f8f9fa;
  border-radius: 6px;
  border: 1px solid #e5e7eb;
  font-weight: 600;
  color: #374151;
  text-align: center;
  transition: all 0.2s ease;
  user-select: none;
  font-size: 0.95rem;
  list-style: none;
}

.reference-card.verbs-card summary::-webkit-details-marker {
  display: none;
}

.reference-card.verbs-card summary::before {
  content: '▶ ';
  display: inline-block;
  margin-right: 0.5rem;
  transition: transform 0.2s ease;
}

.reference-card.verbs-card details[open] summary::before {
  transform: rotate(90deg);
}

.reference-card.verbs-card summary:hover {
  background: #e5e7eb;
  border-color: #d1d5db;
  color: #1f2937;
}

.reference-card.verbs-card details[open] summary {
  background: #2196F3;
  color: white;
  border-color: #2196F3;
  margin-bottom: 1rem;
}

.reference-card.verbs-card details[open] summary::before {
  color: white;
}

.reference-card.proverbs-card .reference-content {
  max-width: none;
  margin: 0;
}

.reference-card.proverbs-card .korean-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.reference-card.proverbs-card .korean-list li {
  border: 1px solid #eee;
  padding: 1.5rem;
  border-radius: 8px;
  background: #fff;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  font-size: 1.1rem;
}

.reference-card.proverbs-card .proverb-meaning {
  margin-top: 0.5rem;
  padding-top: 0.5rem;
  border-top: 1px solid #eee;
  font-size: 1rem;
}

.reference-card.proverbs-card h3 {
  font-size: 1.4rem;
}

/* Usage notes styling */
.usage-note {
  background: #e3f2fd;
  border-left: 4px solid #2196F3;
  padding: 0.75rem;
  margin: 0.5rem 0 1rem 0;
  border-radius: 4px;
  font-size: 0.9rem;
  color: #1565c0;
}

.usage-note strong {
  color: #0d47a1;
}

/* Time subsection styling */
.time-subsection {
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
}

.time-subsection h5 {
  color: #666;
  margin-bottom: 0.3rem;
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.time-subsection:not(:last-child) {
  border-bottom: 1px solid #f0f0f0;
}

/* Make certain cards span full width */
.reference-card.grammar-card,
.reference-card.pronunciation-card {
  grid-column: 1 / -1;
}

/* Responsive design */
@media (max-width: 768px) {
  .reference-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  
  .reference-card {
    margin-bottom: 1rem;
  }
  
  .reference-content {
    padding: 1rem;
    min-height: auto;
  }
  
  .compact-row {
    padding: 0.5rem;
  }
  
  .compact-content {
    grid-template-columns: 1fr;
    gap: 0.25rem;
  }
}

/* Enhanced typography for Korean text */
.compact-row {
  font-family: 'Segoe UI', 'Apple SD Gothic Neo', 'Noto Sans CJK KR', sans-serif;
}

/* Highlight Korean characters */
.compact-row em {
  font-style: normal;
  color: #666;
  font-size: 0.9em;
}

/* Cultural Content Section Styles */
.cultural-content-section {
  background: white;
  border-radius: 10px;
  padding: 2rem;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
  margin-bottom: 2rem;
  scroll-margin-top: 15vh;
}

.cultural-content-section h2 {
  color: #333;
  margin-bottom: 1.5rem;
  border-bottom: 2px solid #eee;
  padding-bottom: 0.5rem;
}

.cultural-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
}

.cultural-card {
  border-radius: 12px;
  padding: 1.5rem;
  border: 2px solid #fff;
  box-shadow: 0 4px 8px rgba(0,0,0,0.15);
  background: #f8f9fa;
}

.cultural-card h3 {
  margin: 0 0 1rem 0;
  font-size: 1.3rem;
  font-weight: bold;
  color: #2196F3;
  text-align: center;
  border-bottom: 2px solid #e9ecef;
  padding-bottom: 0.5rem;
}

.video-links {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.video-link {
  display: block;
  padding: 0.75rem;
  background: white;
  border-radius: 6px;
  text-decoration: none;
  color: #333;
  border: 1px solid #ddd;
  transition: all 0.2s ease;
}

.video-link:hover {
  background: #e3f2fd;
  border-color: #2196F3;
  transform: translateX(2px);
}

.video-title {
  font-weight: 500;
  color: #2196F3;
}

.songs-content {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.song-item {
  background: white;
  padding: 1rem;
  border-radius: 8px;
  border: 1px solid #ddd;
}

.song-item h4 {
  margin: 0 0 0.75rem 0;
  color: #333;
  font-size: 1.1rem;
  border-bottom: 1px solid #eee;
  padding-bottom: 0.5rem;
}

.lyrics {
  font-family: 'Segoe UI', 'Apple SD Gothic Neo', 'Noto Sans CJK KR', sans-serif;
}

.lyric-line {
  margin-bottom: 0.25rem;
  font-size: 0.95rem;
  color: #333;
}

.lyric-line em {
  color: #666;
  font-style: italic;
  font-size: 0.85rem;
}

.lyric-translation {
  margin-bottom: 0.5rem;
  font-size: 0.85rem;
  color: #888;
  font-style: italic;
  padding-left: 1rem;
}

.korean-poem {
  margin-bottom: 1rem;
  padding: 1rem;
  background: #f9f9f9;
  border-radius: 6px;
  border-left: 3px solid #2196F3;
  font-size: 1.05rem;
  line-height: 1.6;
}

.poem-explanation {
  color: #666;
  font-size: 0.9rem;
  text-align: center;
  font-style: italic;
  margin-top: 0.5rem;
}

.inline-author {
  font-style: italic;
  color: #888;
  font-size: 0.85em;
  font-weight: 300;
}

/* Responsive design for cultural section */
@media (max-width: 768px) {
  .cultural-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  
  .cultural-card {
    padding: 1rem;
  }
  
  .cultural-content-section {
    padding: 1rem;
  }
  
  /* Modern minimalistic responsive design */
  .level-container {
    margin-bottom: 1rem;
  }
  
  .level-header {
    padding: 1.5rem;
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
    position: relative;
  }
  
  .level-summary {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
    width: 100%;
  }
  
  .expand-icon {
    position: absolute;
    top: 1rem;
    right: 1rem;
    margin-left: 0;
    width: 2rem;
    height: 2rem;
    font-size: 0.875rem;
  }
  
  .cultural-mini-grid {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
  
  .level-details {
    padding: 1.5rem;
  }
  
  .levels-section {
    padding: 1rem;
  }
  
  .note-item {
    padding: 1rem;
  }
  
  .cultural-mini-card {
    padding: 1rem;
  }
  
  .class-notes-subsection h4,
  .cultural-subsection h4 {
    font-size: 1rem;
  }
  
  .level-info h3 {
    font-size: 1.25rem;
  }
}
</style>

<script>
function toggleLevel(levelId) {
  const content = document.getElementById(levelId + '-content');
  const icon = document.getElementById(levelId + '-icon');
  
  if (content.classList.contains('expanded')) {
    content.classList.remove('expanded');
    icon.classList.remove('rotated');
    icon.textContent = '+';
  } else {
    content.classList.add('expanded');
    icon.classList.add('rotated');
    icon.textContent = '−';
  }
}

// Initialize all levels as collapsed by default
document.addEventListener('DOMContentLoaded', function() {
  // All levels start collapsed - no initialization needed
  // Users can click to expand any level they want to view
});
</script>

---

URL: https://jaskamalkainth.github.io/blog_posts/music.html
Title: Music Is My Only Drug: Piano Pieces I Keep Coming Back To
Description: The piano pieces I return to again and again: Beethoven's Für Elise, Mariage d'Amour, the Love Story theme and a virtuosic Harry Potter medley, with videos.
Published: 2022-01-01
Updated: 2026-10-02

<div class="music-container">
  <div class="hero-section">
    <h1>🎵 Music is my only drug!</h1>
    <p class="subtitle">There's nothing like music to relieve the soul and uplift it.</p>
    <img src="https://raw.githubusercontent.com/Jaskamalkainth/images/master/hqdefault.jpg" alt="Painting of a woman in a white dress playing the piano, in bright orange and yellow brushstrokes" class="hero-image" />
  </div>

  <div class="section">
    <div class="section-header">
      <i class="fa fa-star section-icon"></i>
      <h2>Classical Music Legends</h2>
    </div>
    
    <div class="legends-grid">
      <div class="legend-card">
        <a href="https://raw.githubusercontent.com/Jaskamalkainth/images/master/96ed9b0919b25388599fd3e0dd926db4.jpg" target="_blank" class="image-link">
          <img src="https://raw.githubusercontent.com/Jaskamalkainth/images/master/96ed9b0919b25388599fd3e0dd926db4.jpg" alt="Portrait of Johann Sebastian Bach with his quote: The aim and final end of all music should be none other than the glory of God and the refreshment of the soul." loading="lazy" />
        </a>
      </div>
      
      <div class="legend-card">
        <a href="https://raw.githubusercontent.com/Jaskamalkainth/images/master/Ludwig-van-Beethoven-Quotes.jpg" target="_blank" class="image-link">
          <img src="https://raw.githubusercontent.com/Jaskamalkainth/images/master/Ludwig-van-Beethoven-Quotes.jpg" alt="Portrait of Ludwig van Beethoven with the quote: Music is the mediator between the spiritual and the sensual life." loading="lazy" />
        </a>
      </div>
      
      <div class="legend-card">
        <a href="https://raw.githubusercontent.com/Jaskamalkainth/images/master/mozart_quote_4_new.jpg" target="_blank" class="image-link">
          <img src="https://raw.githubusercontent.com/Jaskamalkainth/images/master/mozart_quote_4_new.jpg" alt="Portrait of Wolfgang Amadeus Mozart with a quote attributed to him: All I insist on, and nothing else, is that you should show the whole world that you are not afraid. Be silent, if you choose; but when it is necessary, speak, and speak in such a way that people will remember it." loading="lazy" />
        </a>
      </div>
    </div>
  </div>

  <div class="section">
    <div class="section-header">
      <i class="fa fa-music section-icon"></i>
      <h2>Musical Masterpieces</h2>
    </div>
    
    <div class="music-grid">
      <div class="music-card">
        <div class="composer-tag">Paul de Senneville</div>
        <h3><i class="fa fa-play-circle"></i>Mariage d'Amour ("Spring Waltz")</h3>
        <p class="card-note">Often mislabelled online as Chopin; it was written by Paul de Senneville in 1978 and made famous by Richard Clayderman.</p>
        <div class="video-container">
          <iframe src="https://www.youtube.com/embed/EFJ7kDva7JE" title="Mariage d'Amour (Spring Waltz), piano" loading="lazy" allowfullscreen></iframe>
        </div>
      </div>

      <div class="music-card">
        <div class="composer-tag">Beethoven</div>
        <h3><i class="fa fa-play-circle"></i>Für Elise</h3>
        <div class="video-container">
          <iframe src="https://www.youtube.com/embed/bP70gBZc564" title="Beethoven: Für Elise, piano" loading="lazy" allowfullscreen></iframe>
        </div>
      </div>

      <div class="music-card">
        <div class="composer-tag">Francis Lai · Richard Clayderman</div>
        <h3><i class="fa fa-play-circle"></i>Love Story</h3>
        <p class="card-note">Francis Lai's theme from the 1970 film <em>Love Story</em>, in Richard Clayderman's piano arrangement (the video credits Beethoven, but it isn't his).</p>
        <div class="video-container">
          <iframe src="https://www.youtube.com/embed/WPChw6DiIkw" title="Love Story theme, piano (Richard Clayderman)" loading="lazy" allowfullscreen></iframe>
        </div>
      </div>

      <div class="music-card">
        <div class="composer-tag">John Williams · Harry Potter</div>
        <h3><i class="fa fa-play-circle"></i>Harry Potter Piano Medley (Virtuosic Cover)</h3>
        <div class="video-container">
          <iframe src="https://www.youtube.com/embed/YI6hpzai-hU" title="Harry Potter piano medley, virtuosic cover by Eshan Denipitiya" loading="lazy" allowfullscreen></iframe>
        </div>
      </div>
    </div>
  </div>
</div>

<style>
.music-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

.hero-section {
  text-align: center;
  margin-bottom: 3rem;
  padding: 2rem;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 12px;
  color: white;
}

.hero-section h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.hero-section .subtitle {
  font-size: 1.2rem;
  font-style: italic;
  opacity: 0.9;
  margin-bottom: 1.5rem;
}

.hero-image {
  width: 100%;
  max-width: 600px;
  height: 300px;
  object-fit: cover;
  border-radius: 8px;
  box-shadow: 0 8px 20px rgba(0,0,0,0.2);
}

.section {
  margin-bottom: 3rem;
}

.section-header {
  display: flex;
  align-items: center;
  margin-bottom: 2rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid rgba(0,0,0,0.1);
}

.section-icon {
  font-size: 1.8rem;
  margin-right: 1rem;
  color: #667eea;
}

.section-header h2 {
  margin: 0;
  font-size: 1.8rem;
  color: #333;
}

.legends-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.legend-card {
  background: white;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  cursor: pointer;
}

.legend-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

.image-link {
  display: block;
  width: 100%;
  height: 100%;
  text-decoration: none;
  position: relative;
}

.image-link::after {
  content: '🔍';
  position: absolute;
  top: 10px;
  right: 10px;
  background: rgba(0,0,0,0.7);
  color: white;
  padding: 5px 8px;
  border-radius: 50%;
  font-size: 12px;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.legend-card:hover .image-link::after {
  opacity: 1;
}

.legend-card img {
  width: 100%;
  height: 200px;
  object-fit: contain;
  object-position: center;
  background: #f8f9fa;
  transition: transform 0.3s ease;
}

.legend-card:hover img {
  transform: scale(1.05);
}

.music-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: 2rem;
}

.music-card {
  background: white;
  border-radius: 12px;
  padding: 1.5rem;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.music-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

.music-card h3 {
  margin-top: 0;
  margin-bottom: 1rem;
  color: #2c3e50;
  font-size: 1.3rem;
  display: flex;
  align-items: center;
}

.music-card h3 i {
  margin-right: 0.5rem;
  color: #667eea;
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---

URL: https://jaskamalkainth.github.io/blog_posts/philosophy-notes.html
Title: Philosophy Timeline: Great Thinkers Through History
Description: A timeline of philosophy from Socrates to contemporary thinkers, with each philosopher's dates, school and one-line answer to why humans do what they do.
Published: 2025-01-27
Updated: 2026-10-02

<div class="research-container">
  <div class="intro-section">
    <h1>Philosophy Timeline: Understanding the Human Mind</h1>
    <p>I'm fascinated by philosophy, psychology, and the study of human mind - what we do, why we do it. This timeline traces the evolution of human thought from ancient wisdom to modern insights about consciousness and behavior.</p>
  </div>

  <div class="my-research">
    <h3>My Research Notes</h3>
    
    <div class="featured-research">
      <h4>📖 Featured Research: Why Do We Do What We Do?</h4>
      <p>I've written a comprehensive exploration of human motivation through the lens of philosophy, tracing how great thinkers from ancient Greece to modern neuroscience have answered this fundamental question about human behavior.</p>
      <p><strong><a href="/blog_posts/whatwedowhywedo.html" class="research-link">→ Read the full research: "Why Do We Do What We Do? A Philosophical Journey Across the Ages"</a></strong></p>
      <p><em>This deep dive connects the philosophical insights from this timeline with modern psychology and neuroscience, exploring how ancient questions about human nature relate to contemporary findings about the mind.</em></p>
    </div>
    
    <div class="ai-research-note">
      <h4>🤖 AI Research Credit</h4>
      <p>This philosophical exploration is enhanced through collaboration with AI research assistants. While AI tools help synthesize and articulate ideas, all perspectives and critical analysis remain my own.</p>
    </div>
    
    <h4>Additional Research Connections to Explore:</h4>
    <ul>
      <li>How Buddhist mindfulness relates to modern cognitive therapy</li>
      <li>Connections between Stoic philosophy and resilience research</li>
      <li>Aristotelian virtue ethics and positive psychology</li>
      <li>Existentialist anxiety and modern understanding of mental health</li>
      <li>Foucault's power analysis and social psychology</li>
      <li>Ancient debates about free will and neuroscience findings</li>
    </ul>
  </div>

  <div class="research-questions">
    <h3>Timeless Questions About Human Nature</h3>
    <ul>
      <li>What drives human behavior - reason, emotion, or something else?</li>
      <li>Are we fundamentally good, evil, or neutral?</li>
      <li>How much of our behavior is determined vs. free?</li>
      <li>What role do social structures play in shaping who we are?</li>
      <li>How has our understanding of consciousness evolved?</li>
      <li>What can ancient wisdom teach us about modern psychology?</li>
    </ul>
  </div>

  <div class="quick-reference">
    <h2>Quick Reference Timeline</h2>
    <div class="reference-grid">
      <div class="reference-period">
        <h3>Ancient Philosophy</h3>
        <span class="period-span">6th Century BCE - 6th Century CE</span>
        <div class="key-figures">Socrates, Plato, Aristotle, Confucius, Buddha, Augustine</div>
        <div class="key-theme">Foundation of human inquiry: virtue, knowledge, suffering, love</div>
      </div>
      
      <div class="reference-period">
        <h3>Medieval Philosophy</h3>
        <span class="period-span">5th - 15th Century</span>
        <div class="key-figures">Thomas Aquinas, Ibn Rushd (Averroes)</div>
        <div class="key-theme">Synthesis of faith and reason</div>
      </div>
      
      <div class="reference-period">
        <h3>Renaissance & Early Modern</h3>
        <span class="period-span">15th - 18th Century</span>
        <div class="key-figures">Descartes, Spinoza, Locke, Hume, Kant</div>
        <div class="key-theme">Rationalism vs. empiricism; foundations of modern thought</div>
      </div>
      
      <div class="reference-period">
        <h3>19th Century</h3>
        <span class="period-span">1800 - 1900</span>
        <div class="key-figures">Hegel, Kierkegaard, Marx, Nietzsche</div>
        <div class="key-theme">Individual existence, social conditions, will to power</div>
      </div>
      
      <div class="reference-period">
        <h3>20th Century</h3>
        <span class="period-span">1900 - 2000</span>
        <div class="key-figures">Freud, Heidegger, Sartre, de Beauvoir, Wittgenstein, Foucault</div>
        <div class="key-theme">Unconscious mind, existentialism, language, power structures</div>
      </div>
      
      <div class="reference-period">
        <h3>Contemporary</h3>
        <span class="period-span">2000 - Present</span>
        <div class="key-figures">Dennett, Nussbaum</div>
        <div class="key-theme">Consciousness, capabilities, modern psychology</div>
      </div>
    </div>
  </div>

  <div class="timeline">
    <div class="timeline-period">
      <div class="period-header">
        <h2>Ancient Philosophy</h2>
        <div class="period-dates">6th Century BCE - 6th Century CE</div>
      </div>
      
      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Socrates</div>
          <div class="philosopher-dates">470-399 BCE</div>
          <div class="philosopher-school">Classical Greek</div>
          <p>"The unexamined life is not worth living." Pioneered the method of questioning to understand human nature and ethics.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>People act wrongly due to ignorance; if we truly know what is good, we will do good.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Plato</div>
          <div class="philosopher-dates">428-348 BCE</div>
          <div class="philosopher-school">Classical Greek</div>
          <p>Explored the nature of reality, knowledge, and the ideal state. Created the theory of Forms and examined the soul's structure.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Human behavior stems from the conflict between reason, spirit, and appetite within the soul.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Aristotle</div>
          <div class="philosopher-dates">384-322 BCE</div>
          <div class="philosopher-school">Classical Greek</div>
          <p>Systematized logic, ethics, and politics. Studied human flourishing (eudaimonia) and virtue ethics.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act to achieve happiness through virtue, which is developed through habit and practice.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Confucius</div>
          <div class="philosopher-dates">551-479 BCE</div>
          <div class="philosopher-school">Chinese Philosophy</div>
          <p>Emphasized moral cultivation, social harmony, and the importance of relationships and ritual.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Human behavior should be guided by virtue, respect for others, and social responsibility.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Buddha (Siddhartha Gautama)</div>
          <div class="philosopher-dates">563-483 BCE</div>
          <div class="philosopher-school">Buddhist Philosophy</div>
          <p>Explored suffering, desire, and the path to enlightenment through understanding the mind.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act from attachment and desire, which causes suffering; liberation comes through mindfulness.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Augustine of Hippo</div>
          <div class="philosopher-dates">354-430 CE</div>
          <div class="philosopher-school">Christian Philosophy</div>
          <p>Integrated Christian theology with philosophy, exploring free will, time, and human nature.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Human actions are driven by love - either love of God (good) or love of self (sin).</p>
          </div>
        </div>
      </div>
    </div>

    <div class="timeline-period">
      <div class="period-header">
        <h2>Medieval Philosophy</h2>
        <div class="period-dates">5th - 15th Century</div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Thomas Aquinas</div>
          <div class="philosopher-dates">1225-1274</div>
          <div class="philosopher-school">Scholasticism</div>
          <p>Synthesized Aristotelian philosophy with Christian doctrine, exploring reason and faith.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act according to our nature, seeking the ultimate good (God) through reason and virtue.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Ibn Rushd (Averroes)</div>
          <div class="philosopher-dates">1126-1198</div>
          <div class="philosopher-school">Islamic Philosophy</div>
          <p>Defended philosophy against religious orthodoxy, emphasizing reason and individual thought.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Human behavior should be guided by reason, which can lead to truth and happiness.</p>
          </div>
        </div>
      </div>
    </div>

    <div class="timeline-period">
      <div class="period-header">
        <h2>Renaissance & Early Modern</h2>
        <div class="period-dates">15th - 18th Century</div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">René Descartes</div>
          <div class="philosopher-dates">1596-1650</div>
          <div class="philosopher-school">Rationalism</div>
          <p>"I think, therefore I am." Established the foundation of modern philosophy through methodical doubt.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act based on clear and distinct ideas; error comes from hasty judgment and unclear thinking.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Baruch Spinoza</div>
          <div class="philosopher-dates">1632-1677</div>
          <div class="philosopher-school">Rationalism</div>
          <p>Developed a deterministic view of reality where everything follows natural laws, including human emotions.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We are driven by emotions and desires; freedom comes from understanding our nature and emotions.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">John Locke</div>
          <div class="philosopher-dates">1632-1704</div>
          <div class="philosopher-school">Empiricism</div>
          <p>Argued that knowledge comes from experience; the mind is a "blank slate" shaped by sensory input.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Our behavior is shaped by experience and education; we can be improved through better environments.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">David Hume</div>
          <div class="philosopher-dates">1711-1776</div>
          <div class="philosopher-school">Empiricism</div>
          <p>Skeptical about reason's power; emphasized the role of habit, custom, and sentiment in human nature.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act more from passion and habit than reason; moral judgments come from feelings, not logic.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Immanuel Kant</div>
          <div class="philosopher-dates">1724-1804</div>
          <div class="philosopher-school">German Idealism</div>
          <p>Synthesized rationalism and empiricism; developed categorical imperative for moral action.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We should act from duty and universal moral laws, not just desire or consequence.</p>
          </div>
        </div>
      </div>
    </div>

    <div class="timeline-period">
      <div class="period-header">
        <h2>19th Century Philosophy</h2>
        <div class="period-dates">1800 - 1900</div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Georg Wilhelm Friedrich Hegel</div>
          <div class="philosopher-dates">1770-1831</div>
          <div class="philosopher-school">German Idealism</div>
          <p>Developed dialectical method; saw history as the progressive unfolding of absolute spirit.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act within historical contexts; consciousness develops through conflict and resolution.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Søren Kierkegaard</div>
          <div class="philosopher-dates">1813-1855</div>
          <div class="philosopher-school">Existentialism</div>
          <p>Emphasized individual existence, choice, and the leap of faith; critiqued systematic philosophy.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act from anxiety about our freedom; authentic existence requires passionate commitment.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Karl Marx</div>
          <div class="philosopher-dates">1818-1883</div>
          <div class="philosopher-school">Historical Materialism</div>
          <p>Analyzed capitalism and class struggle; argued that material conditions shape consciousness.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Our actions are determined by economic and social conditions; consciousness follows material reality.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Friedrich Nietzsche</div>
          <div class="philosopher-dates">1844-1900</div>
          <div class="philosopher-school">Existentialism</div>
          <p>"God is dead." Challenged traditional morality and advocated for creating one's own values.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act from will to power; we must create our own meaning in a meaningless universe.</p>
          </div>
        </div>
      </div>
    </div>

    <div class="timeline-period">
      <div class="period-header">
        <h2>20th Century Philosophy</h2>
        <div class="period-dates">1900 - 2000</div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Sigmund Freud</div>
          <div class="philosopher-dates">1856-1939</div>
          <div class="philosopher-school">Psychoanalysis</div>
          <p>Explored the unconscious mind, revealing hidden motivations behind human behavior.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Much of our behavior is driven by unconscious desires, fears, and childhood experiences.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Martin Heidegger</div>
          <div class="philosopher-dates">1889-1976</div>
          <div class="philosopher-school">Existentialism</div>
          <p>Explored the question of Being; emphasized authenticity and being-toward-death.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act to flee from anxiety about our mortality; authentic existence requires facing this anxiety.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Jean-Paul Sartre</div>
          <div class="philosopher-dates">1905-1980</div>
          <div class="philosopher-school">Existentialism</div>
          <p>"Existence precedes essence." We are condemned to be free and must create our own meaning.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act to escape the overwhelming responsibility of absolute freedom, often in bad faith.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Simone de Beauvoir</div>
          <div class="philosopher-dates">1908-1986</div>
          <div class="philosopher-school">Feminist Existentialism</div>
          <p>"One is not born, but rather becomes, a woman." Examined how social conditioning shapes identity.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Our behavior is heavily influenced by social expectations and power structures we internalize.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Ludwig Wittgenstein</div>
          <div class="philosopher-dates">1889-1951</div>
          <div class="philosopher-school">Analytic Philosophy</div>
          <p>"The limits of my language mean the limits of my world." Explored language and its role in thought.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Our actions are shaped by language games and forms of life that give meaning to our words.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Michel Foucault</div>
          <div class="philosopher-dates">1926-1984</div>
          <div class="philosopher-school">Post-Structuralism</div>
          <p>Analyzed how power shapes knowledge, identity, and behavior through institutions and discourse.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Our actions are shaped by invisible power structures operating through knowledge systems.</p>
          </div>
        </div>
      </div>
    </div>

    <div class="timeline-period">
      <div class="period-header">
        <h2>Contemporary Philosophy</h2>
        <div class="period-dates">2000 - Present</div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Daniel Dennett</div>
          <div class="philosopher-dates">1942-2024</div>
          <div class="philosopher-school">Philosophy of Mind</div>
          <p>Applied evolutionary and computational approaches to consciousness and free will.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>Our behavior emerges from complex neural processes; consciousness is multiple competing narratives.</p>
          </div>
        </div>
      </div>

      <div class="timeline-item">
        <div class="timeline-marker"></div>
        <div class="timeline-content">
          <div class="philosopher-name">Martha Nussbaum</div>
          <div class="philosopher-dates">1947-</div>
          <div class="philosopher-school">Capabilities Approach</div>
          <p>Bridges ancient philosophy with contemporary issues, emphasizing human capabilities and emotions.</p>
          <div class="key-insight">
            <h4>Why We Do What We Do:</h4>
            <p>We act to develop our human capabilities; emotions play a crucial role in moral reasoning.</p>
          </div>
        </div>
      </div>
    </div>
  </div>
</div>

---

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</style>

---

URL: https://jaskamalkainth.github.io/blog_posts/samsung-galaxy-book6-student-guide.html
Title: Galaxy Book6 vs Book6 Pro vs Ultra: Which Should Students Buy?
Description: Galaxy Book6 vs Book6 Pro vs Book6 Ultra for students: processor, display, RAM and storage compared, and which tier fits writing, CS/engineering or design work.
Published: 2026-01-20
Updated: 2026-01-20

# Samsung Galaxy Book6 Series: Which Tier Should Students Buy?

> **Quick answer:** the **Galaxy Book6** is enough for writing, research and browsing; the **Galaxy Book6 Pro** is the pick for CS and engineering students who run IDEs and VMs; the **Galaxy Book6 Ultra** only pays off for sustained heavy work (large datasets, design or video). None of the three has a discrete GPU. Specs are from Samsung India's buy page as of January 2026.

*Disclosure: I work at Samsung R&D Institute India. This is a personal post, not an official Samsung publication; it is based only on Samsung India's public product pages, linked throughout.*

Samsung's current Galaxy Book lineup is a single series split into three configurable tiers, which makes it a genuinely useful case study for students trying to figure out how much laptop they actually need: **Galaxy Book6**, **Galaxy Book6 Pro**, and **Galaxy Book6 Ultra**. Specs below are pulled directly from [Samsung India's Galaxy Book6 Series buy page](https://www.samsung.com/in/computers/galaxy-book/galaxy-book6-series/buy/).

## Spec Comparison

| Variant | Processor | Display | RAM | Storage |
|---|---|---|---|---|
| Galaxy Book6 | Intel Core Ultra 5 (325) | 14.0" | 16GB | 512GB |
| Galaxy Book6 Pro | Intel Core Ultra 7 (356H / 355) | 14.0" or 16.0" | 16GB or 32GB | 512GB or 1TB |
| Galaxy Book6 Ultra | Intel Core Ultra X7 (358H) | 16.0" (touch available) | 32GB | 1TB |

- **OS:** Windows 11 Home (all tiers)
- **Colors:** Gray, Silver
- **Pricing:** Built-to-order — Samsung doesn't list a single fixed price per tier, since it depends on the exact processor/RAM/storage/display combination you configure. [Configure a model and see live pricing →](https://www.samsung.com/in/computers/galaxy-book/galaxy-book6-series/buy/)

## Which Tier Fits Which Student

**Galaxy Book6** — the base tier's 16GB RAM and 512GB storage cover writing, research, browsing, and note-taking comfortably. This is the one to pick if your laptop's job is mostly documents, PDFs, and a browser with too many tabs open.

**Galaxy Book6 Pro** — the sensible middle ground for CS/engineering students: a faster Ultra 7 chip and the option to go up to 32GB RAM / 1TB storage handles heavier IDEs, local dev environments, and running a VM or two without the Ultra tier's price.

**Galaxy Book6 Ultra** — the Ultra X7 chip, 32GB RAM as standard, and a 16.0" touch display option make sense for students doing sustained compile-heavy work, large datasets, or design/video coursework where the extra headroom (and screen real estate) actually gets used.

*(Full computer catalog, including other Samsung lines: [samsung.com/in/computers/all-computers](https://www.samsung.com/in/computers/all-computers/).)*

## The Trade-off to Know Before Buying

None of the three tiers list a discrete GPU in the configuration options above — all rely on integrated graphics. That's fine for coursework, IDEs, and everyday multitasking, but if your program specifically needs GPU-accelerated work (ML training, 3D rendering, certain CAD tools), that's worth checking directly on Samsung's configurator or looking outside this lineup before buying.

👉 **[See current Galaxy Book6 pricing and configure yours →](https://www.samsung.com/in/computers/galaxy-book/galaxy-book6-series/buy/)**

## Frequently asked questions

### Which Galaxy Book6 model is best for students?

For most students the base Galaxy Book6 (Intel Core Ultra 5, 16GB RAM, 512GB) is enough for writing, research and browsing. CS and engineering students who run IDEs, local dev environments or VMs should look at the Galaxy Book6 Pro (Core Ultra 7, up to 32GB RAM and 1TB).

### Do Galaxy Book6 laptops have a dedicated GPU?

None of the Galaxy Book6, Book6 Pro or Book6 Ultra configurations on Samsung India's buy page list a discrete GPU; all use integrated graphics. Check the configurator before buying if you need GPU-accelerated work such as ML training or 3D rendering.

### What is the difference between Galaxy Book6 Pro and Book6 Ultra?

The Ultra uses an Intel Core Ultra X7 (358H), comes with 32GB RAM and 1TB storage as standard, and is 16-inch only with a touch option. The Pro uses a Core Ultra 7, comes in 14-inch or 16-inch, and lets you choose 16GB or 32GB RAM and 512GB or 1TB storage.


---

URL: https://jaskamalkainth.github.io/blog_posts/segment_tree_problems.html
Title: Segment Tree Problems: 20 Practice Problems from Easy to Hard
Description: 20 hand-picked segment tree problems from LightOJ, SPOJ and Codeforces, sorted by difficulty, tagged by technique (lazy propagation, custom merges), with solutions.
Published: 2016-06-08
Updated: 2026-10-02

<div class="pl-hero">
  <div>
    <h1>Segment Tree Problems</h1>
    <p><strong>A segment tree</strong> is a binary tree over an array where each node stores the answer (sum, min, GCD…) for one range, so range queries and updates both run in O(log n).</p>
    <p class="pl-lede"> problems from LightOJ, SPOJ and Codeforces, ordered from first segment tree to hard. Each one is tagged with the technique it teaches and links to my solution. Tick off the ones you solve; your progress is saved in this browser.</p>
  </div>
  <img src="/img/segtree.png" alt="A segment tree built over an array, each node holding the answer for its range" width="220" height="220" loading="lazy">
</div>

<div class="pl" data-store="jk-solved-llms-full-txt">
  <div class="pl-progress" aria-live="polite">
    <div class="pl-bar" role="progressbar" aria-label="Problems solved" aria-valuemin="0" aria-valuemax="" aria-valuenow="0"><i></i></div>
    <span><b class="pl-solved-n">0</b> /  solved</span>
    <button type="button" class="pl-reset" hidden>Reset</button>
  </div>

  <div class="pl-toolbar" role="search">
    <div class="pl-row">
      <input type="search" class="pl-q" placeholder="Search problems" aria-label="Search problems">
    </div>
    <div class="pl-row" role="group" aria-label="Filter by difficulty">
      <button type="button" class="pl-chip pl-hide" aria-pressed="false">Hide solved</button>
      <span class="pl-count" aria-live="polite"> problems</span>
    </div>
  </div>

  <ol class="pl-list">
  </ol>
  <p class="pl-empty" hidden>No problems match. <a href="#" class="pl-clear">Clear filters</a></p>
</div>
<script src="/js/problem_list.js?v=1792922856" defer></script>

## Frequently asked questions

### What is a segment tree?

A segment tree is a binary tree built over an array where each node stores an aggregate (sum, minimum, GCD, and so on) of a contiguous range. It answers range queries and applies point updates in O(log n) time, using O(n) memory.

### What is lazy propagation in a segment tree?

Lazy propagation defers range updates: instead of updating every element in [l, r], you tag the O(log n) nodes that cover the range and push the pending update down to children only when a later query or update visits them. This keeps range updates at O(log n).

### In what order should I solve these segment tree problems?

Top to bottom. The list starts with plain range-minimum and range-sum queries, moves to lazy propagation, then to nodes that store custom merged state (such as the GSS maximum-subarray series), and ends with harder combinations like inclusion–exclusion over 3D toggles.


---

URL: https://jaskamalkainth.github.io/blog_posts/textgrain-watermark-explained.html
Title: textGrain Explained: How OpenAI Watermarks ChatGPT Text
Description: textGrain is OpenAI's text watermark: a secret key and optimal transport tilt token choices within an entropy budget β, and a key-only test detects it.
Published: 2026-10-07
Updated: 2026-10-07

# textGrain Explained: How OpenAI's Text Watermark Works

> **In short:** textGrain is the watermark OpenAI announced on 5 October 2026 for ChatGPT and Codex text in the EU. A secret key splits the vocabulary into hidden blocks and nudges which block the next token comes from, using optimal transport within an entropy budget β. A detector with only the text and the key then runs a Gamma test on the scores.

I read OpenAI's [technical report](https://cdn.openai.com/pdf/e9508624-d767-41b6-a26d-e34ca798ada6/textgrain-entropy-calibrated-watermarking-for-language-model-text.pdf) and built a simulator so I could see each step move. This post explains the idea with as little maths as it needs, then gives the formulas for anyone who wants them. Everything in the "how it works" sections comes from the report; numbers on real-world detection are OpenAI's, as reported at launch.

**Try it first:** the [textGrain watermark simulator](/blog_posts/experiments/textgrain-watermark/) lets you change the key and β for one word, then watch a detector separate a watermarked passage from a plain one.

## What is textGrain?

textGrain is a **statistical text watermark**: it leaves no visible mark and no hidden characters. Instead, it slightly changes *which* tokens the model samples, in a pattern only someone with a secret key can check. A token is a word or part of a word.

What OpenAI announced on 5 October 2026 (as reported by [FoneArena](https://www.fonearena.com/blog/494156/openai-textgrain-watermarking-chatgpt-codex-eu.html) and [Unite.AI](https://www.unite.ai/openai-begins-phased-text-watermarking-under-eu-ai-act-rules/), citing OpenAI's post):

- **Where:** eligible ChatGPT and Codex text output in the **European Union**, rolled out in phases over the following weeks.
- **API:** opt-in for API customers worldwide, off by default.
- **Detection:** not public at launch; access first goes to approved researchers and expert organizations.
- **Open source:** OpenAI says it plans to release textGrain as open source.

The report is by Xiang Li and Qi Long (University of Pennsylvania), Garrett Wen and Xiaohong Chen (Yale), and Arzav Jain, Florent Joly, Mike Lam, Qingquan Song and Weijie Su (OpenAI).

## How does an LLM text watermark work?

A language model writes one token at a time by **sampling** from a next-token probability distribution $$P$$. A watermark replaces plain sampling with sampling that also depends on a pseudorandom value derived from a **secret key** and the last few tokens (the **context window**). The detector recomputes those values from the text and the key, and tests whether the tokens line up with them more often than chance.

Two older designs show the trade-off textGrain is trying to fix:

| Watermark | How it biases sampling | Weak spot |
|---|---|---|
| Red/green list ([Kirchenbauer et al., 2023](https://arxiv.org/abs/2301.10226)) | Adds a bonus to the logits of a keyed "green" half of the vocabulary | Biased: changes the model's distribution on every key |
| Gumbel-max ([Aaronson, 2023](https://simons.berkeley.edu/talks/scott-aaronson-ut-austin-openai-2023-08-17)) | Picks the token with the largest log-probability plus a keyed Gumbel value | Unbiased, but deterministic: same key + same context → same token every time |
| **textGrain** (OpenAI, 2026) | Optimal transport tilts keyed *blocks* of tokens, within entropy budget β | Signal is spread thin: needs a few hundred tokens, and edits erase it |

A watermark is **unbiased** if, averaged over random keys, it gives back exactly the model's distribution $$P$$. Gumbel-max is unbiased, but because one key is reused across many answers, asking the same prompt twice can return the same answer word for word. textGrain keeps the unbiasedness and spends only a chosen fraction of the randomness.

## How textGrain watermarks the next token

The report's running example is the prompt *"The morning was ___"* with six candidate words. My simulator uses the same numbers.

| Token | warm | cold | mild | calm | sunny | bright |
|---|---|---|---|---|---|---|
| Model probability $$P$$ | 0.30 | 0.25 | 0.15 | 0.10 | 0.10 | 0.10 |

One generation step has five parts:

1. **Split the vocabulary into secret blocks.** The key and context window assign every token to one of $$B$$ blocks (3 in the example). Without the key the split looks random. Each block gets the summed probability of its tokens, $$\rho_b$$.
2. **Draw a keyed score table.** For each block $$b$$ and each of $$m$$ equally likely **columns** (4 in the example), the key and context generate a standard Gumbel value $$Z_{bj}$$. High scores mark "favoured" block–column pairs.
3. **Solve a small optimal transport problem.** Find a joint table $$\pi(b, j)$$, a **coupling**, whose rows sum to $$\rho_b$$ and whose columns each sum to $$1/m$$, that puts as much mass on high-score cells as the entropy budget allows.
4. **Let the key pick one column $$J$$.** That column, rescaled, becomes the new block probabilities: favoured blocks get more weight.
5. **Sample a block, then a token inside it** using the model's original relative odds within that block.

Because each column is picked with probability $$1/m$$ and the coupling's rows still sum to $$\rho_b$$, averaging over keys gives back exactly $$P$$. Under one fixed key, though, sampling now leans toward the favoured block, and that lean is the watermark.

Working on $$B$$ blocks × $$m$$ columns instead of the whole vocabulary is what keeps it cheap: each Sinkhorn update costs $$O(Bm)$$ operations, independent of a vocabulary that can have 100,000+ tokens.

## What does the entropy budget β control?

β is the fraction of the model's sampling randomness that textGrain may remove, on average. **β = 0** means no watermark; **β = 0.2** keeps about 80% of the entropy on average; larger β gives a stronger signal and less varied text.

The reason β has such a clean meaning is an identity from information theory. Writing the coupling as $$\pi$$ and the independent (unwatermarked) coupling as $$\rho \otimes u_m$$:

$$
D_{\mathrm{KL}}\left(\pi \,\|\, \rho \otimes u_m\right) = I(W; J) = H(P) - \frac{1}{m}\sum_{j=1}^{m} H\big(Q(\cdot \mid j)\big)
$$

The KL penalty in the transport problem equals the mutual information between the token $$W$$ and the keyed column $$J$$, which equals the average entropy lost. So the optimisation is:

$$
\min_{\pi \in \Pi(\rho,\, u_m)} \sum_{b=1}^{B}\sum_{j=1}^{m} \pi(b,j)\, c(b,j) \quad \text{subject to} \quad D_{\mathrm{KL}}\left(\pi \,\|\, \rho \otimes u_m\right) \le \beta\, H(P)
$$

with cost $$c(b,j) = -G_{bj}$$, the negated standardised Gumbel score. OpenAI's solver runs Sinkhorn iterations on the KL-regularised version and adjusts the regularisation strength λ until the achieved loss is close to $$\beta H(P)$$.

For the example, $$H(P) \approx 1.683$$ nats, so β = 0.4 asks to remove about 0.673 nats. Two limits apply. First, the loss can never exceed $$\min\{H(\rho), \log m\}$$: in my simulator with its default key, the blocks are uneven enough that $$H(\rho) \approx 0.52$$ nats, so the achieved loss stops at about 0.51 nats (30% of $$H(P)$$) no matter how high β goes. The same cap is why a low-entropy step, where the model is nearly sure of the next word, carries almost no watermark. Second, the guarantee is an average over columns, not a promise for every single key.

## How is a textGrain watermark detected?

The detector needs the text, the key and the same settings (tokenizer, $$B$$, $$m$$, context-window rule). It does **not** need the model, the prompt or β. For each position it rebuilds the block split, score table and chosen column, looks up the Gumbel value $$Z_t$$ of the block the actual token is in, and transforms it:

$$
Y_t = -\log\left(1 - F_G(Z_t)\right), \qquad F_G(z) = \exp\left(-e^{-z}\right), \qquad S_n = \sum_{t=1}^{n} Y_t
$$

On text that has nothing to do with the key, each $$Y_t$$ is Exponential(1) with mean 1, so $$S_n$$ follows a Gamma(n, 1) distribution. The detector flags a watermark when $$S_n$$ is above that distribution's $$1-\alpha$$ quantile, which sets the false-positive rate to α under the report's independence assumptions. Watermarked text keeps landing on favoured cells, so its $$Y_t$$ average above 1 and $$S_n$$ climbs past the threshold.

One detail matters in practice: a repeated context window would reuse the same score table, so the detector **scores only the first occurrence** of each distinct context window. The report also notes that a fixed deployed key needs empirical calibration checks; the clean Gamma(n, 1) null is the idealised case.

## How accurate is textGrain detection?

These are OpenAI's launch figures as reported in October 2026, at a 1% false-positive rate; I couldn't access OpenAI's original post directly, and the technical report itself has no experiments.

| Test (as reported, Oct 2026) | Detection rate |
|---|---|
| 200-token passages (psychology text) | about 80% |
| 400-token passages (psychology text) | about 95% |
| 400 tokens, baseline in the editing test | about 92% |
| 400 tokens, 10% of words replaced with synonyms | about 66% |
| 400 tokens, 25% of words replaced with synonyms | about 17% |

Mathematics text was reported to be detected at substantially lower rates, which matches the theory: when the model is nearly certain of each token there is little entropy to spend, so each token carries little evidence. Short replies, code and heavily edited text are the hard cases for any statistical watermark.

## What my simulator simplifies

The [simulator](/blog_posts/experiments/textgrain-watermark/) follows the report's maths but shrinks everything so it runs instantly in a browser:

- a 40-word toy vocabulary and a random toy "model" instead of an LLM;
- $$B = 3$$, $$m = 4$$ for the single-word view (like the report's figure) and $$B = 4$$, $$m = 8$$ for whole passages;
- a 2-token context window and a hash-based pseudorandom function;
- a bisection search for λ instead of the report's multiplicative update;
- a 0.1% false-positive threshold from an approximate Gamma quantile (OpenAI's reported numbers use 1%).

I ran the simulator's own code headless to check it behaves like the theory says. These are toy-model numbers, not predictions for ChatGPT:

| Toy setting (200 runs each) | Watermarked passages detected |
|---|---|
| β = 0, 150 tokens | 0% |
| β = 0.1, 50 tokens / 150 tokens | 9.5% / 43.5% |
| β = 0.3, 50 tokens / 150 tokens | 39% / 94% |
| Unwatermarked, 150 tokens (1,000 runs) | 0.1% flagged (the target false-positive rate) |

Things worth trying: set β to 0 and watch the watermarked passage become indistinguishable; shorten the passage to 30 tokens; or type one wrong character into the detector's key and see the evidence vanish. If you like this kind of "probably, with a known error rate" reasoning, my post on [Bloom filters and their false-positive rate](/blog_posts/bloom_filters.html) uses the same mindset for set membership.

## Sources

- Li, Wen, Chen, Long, Jain, Joly, Lam, Song, Su: [*textGrain: Entropy-Calibrated Watermarking for Language Model Text*](https://cdn.openai.com/pdf/e9508624-d767-41b6-a26d-e34ca798ada6/textgrain-entropy-calibrated-watermarking-for-language-model-text.pdf), OpenAI technical report, 5 October 2026.
- [FoneArena: OpenAI textGrain watermarking for ChatGPT and Codex to roll out in EU](https://www.fonearena.com/blog/494156/openai-textgrain-watermarking-chatgpt-codex-eu.html) (rollout scope, detection figures).
- [Unite.AI: OpenAI begins phased text watermarking under EU AI Act rules](https://www.unite.ai/openai-begins-phased-text-watermarking-under-eu-ai-act-rules/) (rollout scope, detection figures).
- Kirchenbauer et al., [*A Watermark for Large Language Models*](https://arxiv.org/abs/2301.10226), ICML 2023.
- Dathathri et al., [*Scalable watermarking for identifying large language model outputs*](https://www.nature.com/articles/s41586-024-08025-4), Nature 2024 (SynthID Text).
- Cuturi, [*Sinkhorn Distances: Lightspeed Computation of Optimal Transport*](https://arxiv.org/abs/1306.0895), NeurIPS 2013.

## Frequently asked questions

### Does ChatGPT watermark its text?

As of October 2026, OpenAI says it is adding textGrain watermarks to eligible ChatGPT and Codex text output in the European Union, rolled out in phases over the following weeks. API customers worldwide can opt in; it is off by default for them. Outside the EU, ChatGPT text is not covered by this first rollout.

### Can I check whether a text has a textGrain watermark?

Not yourself, as of October 2026. Detection needs OpenAI's secret key, and OpenAI is giving detector access first to approved researchers and expert organizations, case by case. OpenAI has said it plans to release textGrain as open source, which would let others watermark their own models with their own keys, but not detect ChatGPT text without OpenAI's key.

### Can paraphrasing remove a textGrain watermark?

It weakens it a lot. In OpenAI's reported tests on 400-token passages, replacing 10% of words with synonyms dropped detection from about 92% to 66%, and replacing 25% dropped it to 17%. Every edited token loses its evidence, so a thorough rewrite by a person or another model can push the score back to what unwatermarked text produces.

### Does textGrain make ChatGPT's answers worse?

It is designed not to. Averaged over keys, the token distribution is exactly the model's own, so the watermark is unbiased. The cost is randomness: the entropy budget β caps the average share of sampling entropy removed, so β = 0.2 keeps about 80% of it on average. Regenerating an answer still gives different text, unlike Gumbel-max watermarks.

### How is textGrain different from Google's SynthID Text?

Both are keyed, unbiased statistical watermarks that a detector checks with the key. SynthID Text, published in Nature in 2024, uses tournament sampling. textGrain instead solves a small entropy-regularized optimal transport problem over blocks of the vocabulary, which gives one knob, β, with an exact meaning: the average fraction of sampling entropy given up for the signal.


---

URL: https://jaskamalkainth.github.io/blog_posts/whatwedowhywedo.html
Title: Why Do We Do What We Do? A Philosophical Journey Across the Ages
Description: What drives human action? How Plato, Aristotle, the Stoics, Augustine, Hume, Kant, Nietzsche, Sartre and cognitive science answer it, plus a personal reflection.
Published: 2025-01-27
Updated: 2026-10-02

<div class="philosophy-research">
  <div class="research-header">
    <h1>Why Do We Do What We Do?</h1>
    <h2>A Philosophical Journey Across the Ages</h2>
    <div class="research-intro">
      <p><strong>In short:</strong> philosophers have explained human action as the pursuit of a perceived good (Plato, Aristotle, the Stoics), as love directed toward an ultimate end (Augustine, Aquinas), as passion served by reason (Hume), as duty (Kant), as will to power (Nietzsche), as material conditions (Marx), as radical freedom (Sartre), and, in today's cognitive science, as partly unconscious processes. This essay walks through each era and ends with what it means for my own choices.</p>
      <p><em>I often catch myself wondering what really drives my actions. Is it desire, duty, survival, love, or something deeper? This simple question—"Why do we do what we do?"—has followed humanity through the ages. Philosophers from ancient Athens to modern science have all taken turns trying to answer it. Each era's thinkers, in their own way, held up a mirror to human motives. In this journey through time, I reflect on how different schools of thought have grappled with the engines of human action, and what their insights mean for us today.</em></p>
    </div>
  </div>

  <div class="table-of-contents">
    <h3>📚 Journey Through Time</h3>
    <ul>
      <li><a href="#personal-reflection">Personal Reflection: "Stay Curious and Stay Alive"</a></li>
      <li><a href="#ancient-philosophy">Ancient Philosophy: Reason, Desire, and the Good</a></li>
      <li><a href="#medieval-insights">Medieval Insights: Will, Love, and Divine Purpose</a></li>
      <li><a href="#enlightenment-reason">Enlightenment and Reason: The Rise of the Rational Self</a></li>
      <li><a href="#19th-century">19th Century: Will, Power, and Social Drives</a></li>
      <li><a href="#20th-century">20th Century Currents: Freedom, Pragmatism, and Analysis</a></li>
      <li><a href="#contemporary-views">Contemporary Views: Mind Sciences and Philosophical Psychology</a></li>
    </ul>
  </div>

  <div class="research-content">
    <section id="personal-reflection" class="era-section">
      <div class="era-header">
        <h2>🎯 Personal Reflection: "Stay Curious and Stay Alive"</h2>
      </div>
      <div class="content-text">
        <p><em>In a personal reflection:</em> when I think about why <em>I</em> do what I do in light of all this, I see fascinating layers in my daily actions. I make coffee each morning, not just because I'm habitually craving caffeine (pragmatic habit, physiological drive), but also because the ritual itself brings a meditative start to my day. The simple act of boiling water and mixing my black coffee, stripped of any unnecessary complexity, becomes a moment of clarity and focus, perhaps reflecting a broader philosophical preference for essence over ornament.</p>

        <p>I find myself drawn to helping friends and colleagues, partly because I empathize (emotional intuition) and because I've adopted a value that meaningful connections matter (second-order endorsement). But there's also a deeper satisfaction in being part of a supportive community, perhaps touching on what Aristotle called the social nature of human flourishing. This extends to my approach to learning and problem-solving. I immerse myself in coding challenges and complex problems not just for practical skill-building, but because there's a profound joy in the intellectual pursuit itself (a blend of Nietzsche's will to power and Aristotle's natural human curiosity).</p>

        <p>My eclectic taste in music, spanning different genres and languages, reflects both a desire for aesthetic pleasure and a deeper yearning to connect with diverse human experiences. Whether it's classical, jazz, or folk music from across the globe, each genre offers a unique lens into human expression and emotion. And yes, I often find myself overthinking small decisions or interactions, a tendency that can be both a curse and a blessing. It's the philosopher's burden: to seek meaning even in mundane moments, though sometimes this very seeking can overshadow the simple joy of being.</p>

        <p>Yet, I also use reasoning to discern what is true and good, and that rational motive can override others. A touch of Kantian duty pushing me to write clean, maintainable code rather than quick hacks, or to give honest feedback instead of just pleasing others. All this occurs while navigating the practical demands of a tech career (Marx's material dimension) and the influence of modern digital culture.</p>

        <p><strong>This multifaceted nature of my motivations is both humbling and empowering.</strong> Humbling because it shows how many factors, from caffeine cravings to cultural conditioning, influence my daily choices. I can't claim to be purely rational in my decisions. Empowering because understanding these various drives gives me a chance to align them better with my values and growth. As the ancient oracle advised, "Know thyself," whether in code, coffee, or conversation, that remains a lifetime's journey.</p>
      </div>
    </section>

    <section id="ancient-philosophy" class="era-section">
      <div class="era-header">
        <h2>Ancient Philosophy: Reason, Desire, and the Good</h2>
        <div class="era-period">6th Century BCE - 6th Century CE</div>
      </div>

      <div class="philosopher-quote">
        <blockquote>
          <p><em>Plato and Aristotle in Raphael's <strong>School of Athens</strong>, symbolizing the ancient quest to understand human motives.</em></p>
        </blockquote>
      </div>

      <div class="content-text">
        <p>In ancient Greece, philosophers began our story by rooting human action in a search for the <strong>good</strong>. <strong>Plato</strong> traced human behavior to three sources: desire, emotion (spirit) and knowledge (reason). In the <em>Republic</em> he described the soul as tripartite, and in the <em>Phaedrus</em> he pictured it as a charioteer of reason struggling to rein in two horses: a noble, spirited one and an unruly one of appetite. (The often-shared line "Human behavior flows from three main sources: desire, emotion, and knowledge" summarizes this view but does not appear in Plato's dialogues.)</p>

        <p>Why do we do what we do, according to Plato? Because our soul's parts push and pull us – our <strong>desires</strong> draw us toward what seems good, our <strong>emotions</strong> spur us or hold us back, and our <strong>reason</strong> seeks a higher understanding of the true Good. If reason rules, we act wisely; if appetite or anger takes over, we might stray. Plato believed no one <em>knowingly</em> does wrong – we err out of ignorance, mistaking what is truly good. This optimistic view implies that if we <em>know</em> the Good, we will do it. Knowledge, in this sense, is motivation.</p>

        <p><strong>Aristotle</strong> took up a similar theme but added nuance. For Aristotle, every action aims at some <em>end</em> or <em>purpose</em>, and ultimately at <strong>happiness (eudaimonia)</strong>. <em>"Every art and every inquiry, and similarly every action and pursuit, is thought to aim at some good,"</em> he wrote at the opening of the <em>Nicomachean Ethics</em>, meaning we always act for the sake of something we perceive as good. If you go to work, maybe it's for money (a proximate end), which in turn is for security or pleasure, all leading toward the ultimate end of well-being or fulfillment.</p>

        <p>Aristotle grounded this in a natural teleology: just as a seed acts to become a tree, a person acts to achieve flourishing. We do what we do <em>because</em> we seek our <em>"proper good,"</em> whether we realize it or not. He also argued that <strong>habits</strong> shape our character: we become just by doing just acts. (The famous line <em>"we are what we repeatedly do"</em> is Will Durant's 1926 summary of this idea, not Aristotle's own words.) This hints that virtuous actions, repeated, spring from a trained motivation to be excellent.</p>

        <p>Meanwhile, the <strong>Stoics</strong> offered a more stern answer to the question of action. They agreed that humans are rational beings and claimed that a <em>life according to nature</em> (i.e. aligned with reason and virtue) is the ultimate purpose of action. A Stoic might say that <em>why</em> a wise person acts is straightforward: to exercise virtue, the only true good.</p>

        <p>The motivations behind human actions are understood in terms of <strong>assent</strong> to impressions – we experience desires and aversions, but it is our judgment that assents (or not) to acting on them. Wrong actions, they thought, come from faulty judgment rather than malice. <em>"They do wrong through ignorance and unintentionally,"</em> wrote the Stoic emperor Marcus Aurelius, sounding much like Socrates.</p>
      </div>

      <div class="key-insights">
        <h4>🔑 Key Ideas of the Ancient Era:</h4>
        <ul>
          <li>Human action aims at a <em>perceived good</em> – even bad actions stem from a mistaken view of what is good.</li>
          <li>The struggle between <strong>reason</strong> and <strong>desire</strong> is central. Plato's reason vs. appetite, or Stoic rational judgment vs. passion, highlight an internal dynamic directing what we do.</li>
          <li><strong>Virtue</strong> was seen as aligning one's will with reason: for Aristotle and the Stoics, to act rightly is to act in accordance with reason/nature, which leads to genuine happiness.</li>
        </ul>
      </div>
    </section>

    <section id="medieval-insights" class="era-section">
      <div class="era-header">
        <h2>Medieval Insights: Will, Love, and Divine Purpose</h2>
        <div class="era-period">5th - 15th Century</div>
      </div>

      <div class="content-text">
        <p>As philosophy moved into the Medieval era, the question of human motivation took on a theological flavor. Thinkers like <strong>Saint Augustine</strong> and <strong>Saint Thomas Aquinas</strong> blended classical ideas with Christian doctrine, asking not just <em>why</em> we act, but how our actions relate to God's plan and our ultimate salvation.</p>

        <p>For <strong>Augustine</strong>, the restless heart of human motivation is <strong>love</strong>. In his view, <em>what</em> you love defines <em>why</em> you act: <em>"amor meus, pondus meum"</em> – "My love is my weight," he writes, <em>by it I am carried wherever I go</em>. This beautiful metaphor suggests that love is the gravity of the soul. Why do we do what we do? Because we are pulled by the weight of our affections.</p>

        <p>Augustine saw the whole drama of life as a conflict between love of God and love of worldly things. If we love God (the highest good), our actions will tend toward charity and virtue. If we let disordered loves (for power, pleasure, self) rule us, we will act wrongly. In stories like his famous youthful theft of pears, Augustine analyzed his own motive and found it stemmed from a perverse thrill in doing wrong – a misdirection of love.</p>

        <p><strong>Aquinas</strong>, writing later in the High Middle Ages, systematized the question of motivation under his grand synthesis of Christian theology with Aristotelian philosophy. He echoes Aristotle: <em>"Every agent acts for an end,"</em> and for human beings that ultimate end is <strong>beatitudo</strong> – the blessed happiness of union with God.</p>
      </div>

      <div class="key-insights">
        <h4>🔑 Key Ideas of the Medieval Era:</h4>
        <ul>
          <li><strong>Love orders actions:</strong> What we love determines what we do. Disordered loves lead to bad actions, rightly ordered love (of God) leads to righteous action.</li>
          <li><strong>Every action has an ultimate end:</strong> Medieval thinkers agree with antiquity that all acts aim at a final good (ultimately, reunion with the divine).</li>
          <li><strong>Free will and grace:</strong> Humans have the freedom to choose, but our will needs illumination and help. The motive force of action isn't just mechanical; it's deeply personal and spiritual.</li>
        </ul>
      </div>
    </section>

    <section id="enlightenment-reason" class="era-section">
      <div class="era-header">
        <h2>Enlightenment and Reason: The Rise of the Rational Self</h2>
        <div class="era-period">17th - 18th Century</div>
      </div>

      <div class="content-text">
        <p>The Enlightenment of the 17th and 18th centuries shifted focus toward human <strong>reason</strong> and the individual mind. Philosophers in this era asked: are we fundamentally rational actors, or driven by passion? As scientific thinking rose, explanations of behavior began to look for <em>natural</em> (not just supernatural) causes.</p>

        <p><strong>Descartes</strong>, a 17th-century rationalist, straddled old and new. Famously, he said <em>"I think, therefore I am,"</em> putting consciousness at the center of human identity. Descartes was intrigued by how the <strong>passions</strong> (emotions/desires) move us, yet he believed reason was meant to hold the reins.</p>

        <p>Then comes <strong>David Hume</strong>, the great empiricist, who turned Descartes' view upside down. Hume boldly claimed that <em>reason alone is not the motive for any action</em>. Instead, passions are the engine of all our deeds; without them we would lack any motivation at all. In his <em>Treatise of Human Nature</em> (1739–40) he put it bluntly: <em>"Reason is, and ought only to be the slave of the passions."</em></p>

        <p><strong>Kant</strong>, coming in at the end of the 18th century, tried to rescue the power of reason at least in the moral realm. Immanuel Kant famously drew a line between <strong>inclinations</strong> (our desires and emotions) and <strong>duty</strong> (the moral law dictated by reason). He answered our question on two levels: for ordinary choices, yes, we often act from self-interest or desire; but for <em>moral</em> actions, Kant argued the only valid motive is <strong>good will</strong>.</p>
      </div>

      <div class="key-insights">
        <h4>🔑 Key Ideas of the Enlightenment Era:</h4>
        <ul>
          <li><strong>Passions vs. Reason:</strong> Hume's dictum that reason is the slave of passions set one extreme (emotion drives all). Kant's deference to duty set the other (reason <em>ought</em> to drive moral action).</li>
          <li><strong>Emergence of the individual will:</strong> Descartes and Kant emphasized the <strong>autonomy</strong> of the thinking self – the idea that we can deliberately choose why we act.</li>
          <li><strong>Naturalistic explanations:</strong> Enlightenment thought started to "demystify" human action, looking for causes in human nature rather than solely in divine will.</li>
        </ul>
      </div>
    </section>

    <section id="19th-century" class="era-section">
      <div class="era-header">
        <h2>19th Century: Will, Power, and Social Drives</h2>
        <div class="era-period">1800 - 1900</div>
      </div>

      <div class="content-text">
        <p>The 19th century saw an explosion of new ideas about human motivation, influenced by the tumult of the industrial age, political revolutions, and scientific advancements. Philosophers during this era—figures like <strong>Friedrich Nietzsche</strong>, <strong>Karl Marx</strong>, and <strong>Søren Kierkegaard</strong>—broke with many past assumptions.</p>

        <p>Enter <strong>Nietzsche</strong>, who put forward one of the most provocative answers: behind all human actions lies the <strong>Will to Power</strong>. For Nietzsche, <em>every</em> living thing, whether it realizes it or not, strives to expand its power, to assert itself. He argued that this will to power offers a deeper explanation of human behavior than earlier theories that focused on survival or happiness.</p>

        <p>On a very different front, <strong>Karl Marx</strong> approached human behavior through the lens of <strong>material conditions and class</strong>. Marx essentially relocated the "why" of human actions from individual minds to the structure of society. In his view, the broad patterns of what people do (especially in groups) are driven by economic forces and relations of production.</p>

        <p>Meanwhile, <strong>Kierkegaard</strong> in Denmark delved into the <em>inner</em> dimension of motivation, arguably kicking off existentialist thought. He didn't look to power or economics, but to the individual's <strong>relationship with meaning, self, and God</strong>. Kierkegaard spoke of different "stages of life" – the <strong>aesthetic</strong>, <strong>ethical</strong>, and <strong>religious</strong> – each with its own answer to why we act.</p>
      </div>

      <div class="key-insights">
        <h4>🔑 Key Ideas of the 19th Century:</h4>
        <ul>
          <li><strong>Underlying drives:</strong> Philosophers posited fundamental forces like <em>will to power</em> (Nietzsche) beneath conscious motives, suggesting our actions trace back to deep, often unconscious drives.</li>
          <li><strong>Socio-economic motives:</strong> Human behavior is not in a vacuum; Marx showed how much factors like class, labor, and economic need shape our goals.</li>
          <li><strong>Individual authenticity:</strong> With Kierkegaard, the importance of personal meaning came to fore. The motives that matter are those aligned with one's chosen values or faith.</li>
        </ul>
      </div>
    </section>

    <section id="20th-century" class="era-section">
      <div class="era-header">
        <h2>20th Century Currents: Freedom, Pragmatism, and Analysis</h2>
        <div class="era-period">1900 - 2000</div>
      </div>

      <div class="content-text">
        <p>The 20th century, marked by world wars, rapid scientific progress, and global ideological clashes, brought yet new angles. Three broad movements in philosophy tackled our question in different ways: <strong>existentialism</strong> (focused on individual freedom and meaning), <strong>pragmatism</strong> (focused on practical consequences and habits), and <strong>analytic philosophy</strong> (focused on language, logic, and the mechanics of mind).</p>

        <p>The <strong>existentialists</strong> (like <strong>Jean-Paul Sartre</strong>, <strong>Simone de Beauvoir</strong>, <strong>Albert Camus</strong>) inherited Kierkegaard's torch of personal authenticity but usually without a theistic framework. For them, human beings are condemned to <strong>freedom</strong> – there is no preset answer to why we must act, so we have to choose it for ourselves.</p>

        <p>Switch to <strong>pragmatism</strong>, an American-born philosophy with figures like <strong>William James</strong> and <strong>John Dewey</strong>. Pragmatists were less concerned with metaphysical ultimates and more with <strong>what works</strong> in human life. They effectively answer "why do we do what we do?" with <strong>because it is useful or makes a difference to us</strong>.</p>

        <p>Finally, the <strong>analytic philosophers</strong> of the 20th century took a more fine-grained approach, dissecting the language and logic of how we explain actions. They asked not so much "What ultimate force drives action?" but "What does it <em>mean</em> to have a reason or motive? How do reasons explain actions?"</p>
      </div>

      <div class="key-insights">
        <h4>🔑 Key Ideas of the 20th Century:</h4>
        <ul>
          <li><strong>Radical freedom and responsibility:</strong> Existentialists assert that ultimately <em>we</em> give our lives motives and meaning. Even in absurd conditions, we can choose our reason for acting.</li>
          <li><strong>Practical and empirical turn:</strong> Pragmatists and psychologists focus on <em>how</em> our motives operate in real life – through habits, conditioned responses, and practical decision-making.</li>
          <li><strong>Analytic clarity:</strong> The fine dissection of action shows the interplay of belief, desire, and intention. It emphasizes that asking "why" can mean seeking a person's reasoning.</li>
        </ul>
      </div>
    </section>

    <section id="contemporary-views" class="era-section">
      <div class="era-header">
        <h2>Contemporary Views: Mind Sciences and Philosophical Psychology</h2>
        <div class="era-period">2000 - Present</div>
      </div>

      <div class="content-text">
        <p>Standing in the 21st century, we have a more interdisciplinary understanding of human behavior than ever before. <strong>Cognitive science</strong>, <strong>neuroscience</strong>, and <strong>evolutionary psychology</strong> provide vast data on <em>how</em> and <em>why</em> humans (and other animals) act. Contemporary philosophers often engage with these findings, creating a field one might call <em>philosophical psychology</em> or philosophy of mind in action.</p>

        <p>One significant contemporary insight is the role of the <strong>unconscious</strong>. Research strongly suggests that a lot of our decision-making happens <em>below the surface</em> of conscious reasoning. For instance, psychologists have documented phenomena like implicit biases (attitudes that affect our actions without our awareness) and heuristics (mental shortcuts that operate automatically).</p>

        <p><strong>Neuroscience</strong> adds another layer, connecting motivations to brain regions and chemicals. We know dopamine pathways are involved in reward and thus in motivating seeking behavior. We know the amygdala can trigger fight-or-flight actions out of fear. We've even identified "mirror neurons" that might explain empathetic motivations.</p>

        <p><strong>Philosophical psychology</strong> today often focuses on concepts like <strong>intention, agency, and identity</strong>. For instance, Harry Frankfurt's theory of persons distinguishes between first-order desires (simple wants) and second-order desires (wants about our wants). His idea was that what we <em>truly</em> want – and thus what we act on when we are being our genuine selves – is determined by these higher-order volitions.</p>
      </div>

      <div class="key-insights">
        <h4>🔑 Key Trends of the Contemporary Era:</h4>
        <ul>
          <li><strong>Interdisciplinary integration:</strong> We combine insights from neuroscience (unconscious processes), psychology (behavioral motivations), and philosophy (normative reasons, agency) to get a fuller answer.</li>
          <li><strong>Self-awareness and revision:</strong> There's emphasis on becoming aware of <em>why</em> we act (mindfulness, therapy, reflection) so we can change harmful patterns.</li>
          <li><strong>Continued mystery of the will:</strong> Despite all we know, there's still debate on whether we have free will or are determined by causes. The "why" of action edges into the "how much choice do we really have" question.</li>
        </ul>
      </div>
    </section>

    <div class="sources-section">
      <h3>📚 Key Sources & Influences</h3>
      <ul>
        <li>Plato's tripartite soul and the role of reason, emotion, and desire</li>
        <li>Aristotle's theory that all human action aims at a perceived good</li>
        <li>Marcus Aurelius (Stoicism) on people erring through ignorance</li>
        <li>Augustine's concept of love as the weight that moves us</li>
        <li>Aquinas on every agent acting for an end (ultimate end in God)</li>
        <li>Descartes on passions as motivating impulses toward perceived goods</li>
        <li>Hume's assertion that reason is the slave of the passions</li>
        <li>Kant's argument that only duty should motivate moral action</li>
        <li>Nietzsche's will to power as explanation of human behavior</li>
        <li>Marx's view of material conditions determining human activity</li>
        <li>Kierkegaard's stages of life (aesthetic, ethical, religious) motives</li>
        <li>Sartre's emphasis on freedom and responsibility for all one's actions</li>
        <li>Camus on embracing the struggle (the happy Sisyphus)</li>
        <li>William James on habit and action (pragmatism)</li>
        <li>Anscombe and Davidson on reasons as explanations for action</li>
        <li>Cognitive science on unconscious initiation of action (Libet findings)</li>
      </ul>
    </div>
  </div>
</div>

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## Frequently asked questions

### Why do humans do what they do, according to philosophers?

There is no single answer. Ancient thinkers (Plato, Aristotle, the Stoics) said we act for a perceived good; medieval thinkers (Augustine, Aquinas) pointed to love and an ultimate end; Hume argued passions, not reason, drive action; Kant held that moral action should come from duty; Nietzsche proposed the will to power; existentialists like Sartre said we are free and responsible for every choice; and cognitive science adds unconscious processes that start actions before we are aware of deciding.

### What did Hume mean by "reason is the slave of the passions"?

In A Treatise of Human Nature, Hume argued that reason alone can never motivate action. Reason tells us what is true and how to get what we want, but the wanting itself comes from passions (desires and emotions), so reason only serves them.

### Did Aristotle say "we are what we repeatedly do"?

Not in those words. The line comes from Will Durant's 1926 book The Story of Philosophy, summarizing Aristotle's view in the Nicomachean Ethics that virtues are formed by habit: we become just by doing just acts.