ShellLite Chess Engine and Lichess Bot

A chess engine built entirely in the ShellLite programming language, along with a Lichess Bot Bridge integration.

Features

• Universal Chess Interface compliant engine loop
• Optimised search using Negamax with Alpha Beta Pruning and Transposition Table caching
• Tactical evaluation featuring Piece Square Tables and Delta Pruning
• Custom legal capture generator for quiescence search
• Lichess integration with automatic reconnection on stream disconnections

Architecture

The system consists of two primary components.

1. The ShellLite Chess Engine: Written in ShellLite, implementing the board representation, move generation, and tactical search. It communicates using the standard Universal Chess Interface protocol.
2. The Lichess Bot Bridge: A multithreaded Python application that streams challenges and game events from Lichess, automatically spawning separate, isolated ShellLite engine processes to calculate and make moves for each game.

Requirements

• Python 3.10 or higher
• Requests library
• ShellLite interpreter

Installation and Setup

1. Clone this repository to your local machine.
2. Install the required Python dependencies: pip install shell-lite pip install requests
3. Copy the configuration template file: copy lichess_config.json.example lichess_config.json
4. Edit lichess_config.json and replace YOUR_LICHESS_BOT_TOKEN_HERE with your private Lichess Bot API token.

Running the Engine Locally

To run and test the engine locally via the Universal Chess Interface CLI:

• On Windows, run the run_engine.bat file.
• On Linux or macOS, run: shl main.shl OR shl run main.shl

Running the Lichess Bot

To start the bot and connect it to Lichess:

• On Windows, run the run_lichess.bat file.
• On Linux or macOS, run: python lichess_bot.py

ENJOY!

License: MIT