Boychesser

A very small C# chess engine written for Sebastian Lague's Tiny Chess Bots Challenge. Estimated to be around 2750 Elo on the CCRL Blitz list.

Features

Board representation

Based entirely on Sebastian Lague's framework

Search

Principal variation search
Quiescence search (integrated with main search)
Transposition table
Aspiration windows
Pruning
- Null move pruning
- Reverse futility pruning
- Delta pruning
- Futility pruning
- Late move pruning
Reductions
- Late move reduction
- History reduction
- Internal iterative reduction
Extensions
- Check extension
Move ordering
- TT move
- MVV-LVA
- History heuristic (with gravity)

Evaluation

Phased evaluation
Material
Mirrored piece square tables
King-relative pawn
Slider mobility
Virtual queen mobility
Friendly pawns in front of a piece
Tempo
Tuned on an evenly-mixed combination of Frozenight NNUE data and lichess-big3-resolved

Time management

Based on a fixed percentage of remaining time
Aborts after an iteration if a "soft" limit is exceeded
Aborts during an iteration if a "hard" limit is exceeded