GCE - G Chess Engine

A chess engine written in C99 with UCI protocol support, a web-based GUI, and a live presence on Lichess.

Play Against It

• Lichess: Challenge TheGBot -- note that it may sometimes be offline as it runs on a local machine.
• Web UI: Run the included web server for a full browser-based interface with drag-and-drop, move animations, sound effects, and real-time engine analysis.

Features

Engine

• Bitboard-based board representation with incremental Zobrist hashing
• Negamax search with alpha-beta pruning
• Iterative deepening with aspiration windows
• Principal Variation Search (PVS)
• Late Move Reductions (LMR)
• Null move pruning
• Quiescence search with delta pruning
• Transposition table (1M entries)
• Move ordering: TT move, MVV-LVA, killer heuristic, history heuristic
• Check extensions
• Piece-square tables, bishop pair bonus, pawn structure evaluation (doubled/isolated/passed pawns), king safety (pawn shield), and mobility scoring
• Time management with support for fixed depth, fixed movetime, and clock-based allocation

UCI Protocol

Implements the Universal Chess Interface protocol. Supports position, go (with depth, movetime, wtime/btime/winc/binc, movestogo, infinite), stop, ucinewgame, and more. Compatible with any UCI-compliant GUI (Arena, CuteChess, etc.).

Web Interface

A self-contained browser UI served by a Python/Flask backend that communicates with the engine over WebSocket:

• Drag-and-drop piece movement (mouse and touch)
• Move animations and programmatic sound effects (Web Audio API, no audio files)
• Real-time thinking info display (depth, nodes, kn/s, PV line)
• Top 5 move analysis
• Evaluation bar, move history, captured pieces
• Auto-reply mode, board flipping, undo
• Keyboard shortcuts: Space/Enter (engine), Z (undo), F (flip), N (new game), T (top moves)

Building

Requires GCC and a POSIX environment (Linux/macOS).

make

Usage

Interactive CLI

./gce

Play by entering moves in SAN notation (e.g. e4, Nf3, O-O). Type eval to see the current evaluation or top to see the top moves.

UCI Mode

./gce --uci

Or type uci at the interactive prompt. This is the mode used by chess GUIs and the web interface.

Web Interface

cd web
pip install -r requirements.txt
python server.py

Then open http://localhost:8080 in your browser.

Project Structure

├── main.c          # Entry point, interactive CLI
├── board.c/h       # Position representation, FEN parsing, Zobrist hashing
├── attack.c/h      # Attack tables, sliding piece ray generation
├── movegen.c/h     # Move generation, SAN/coordinate parsing
├── move.c/h        # Make-move logic, game state detection
├── engine.c/h      # Search, evaluation, transposition table
├── uci.c/h         # UCI protocol implementation
├── Makefile        # Build configuration
└── web/
    ├── server.py       # Flask + WebSocket backend
    ├── index.html      # Single-page frontend (~1150 lines)
    ├── requirements.txt
    └── img/            # SVG piece assets

License

GPLv3