Unity Chess Engine

A simple 2D chess engine built in Unity C# from scratch. This project is a personal experiment to build a functional chess bot using Minimax with Alpha-Beta pruning and a fully working move logic system. This entire project was done independently with no guidance and was inspired by Sebastian Lague Coding Adventure: Chess, particularly the Minimax Video.

Engine Strength

• Estimated ELO: around 1000 (based on over 40 manually played games against various levels of Stockfish)
• Search depth: up to 3 plies with acceptable speed
• Depth 4 works but becomes noticeably slow due to lack of search optimizations
• Uses predefined book moves and book move responses for the first move
• Includes positional bonuses so pieces make safer and more stable moves
• Extensively tested through actual games to verify that no illegal moves occur and all legal moves are playable

Game Features

• Play as White, Black, or Random
• Multiple timer options available (similar to common chess time controls)
• Undo and Reset buttons for testing and casual play
• Simple 2D interface with fully working move logic

Technical Details

• Engine Type: Minimax with Alpha-Beta Pruning
• Evaluation: Material plus positional bonuses based on piece-square placement
• Depth Limit: Adjustable, practically capped at 3 for performance
• Implementation: Built in Unity 2D
• Rules: Supports standard chess rules including castling, en passant, and promotion

Download

You can download the last working builds of the game here:

• Windows build (7z)
• Linux build (7z)

Unzip the archive for your platform and run the executable to play.

How to Run

1. Clone the repository:

   git clone https://github.com/hanimuhamed/chess.git

2. Open the project in Unity (version 6000.0.32f1 or later is recommended)

3. Run the MainMenu scene to start the game

Testing

All testing has been done through gameplay to verify that:

• No illegal moves occur
• All legal moves are supported
• Engine responds correctly
• Opening moves are applied as intended

Code Quality Disclaimer

The code works as intended but is messy and not well structured.
It is not refactored and I have avoided changing it further since it already behaves the way I want.

Roadmap

• Optimize search for deeper ply levels
• Improve evaluation heuristics
• Refactor the codebase
• Improve GUI polish and animations

Contributing

Pull requests are welcome.
Bug fixes, performance improvements, and code cleanups are encouraged.

License

This project is released under the MIT License.