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https://github.com/andrewjh271/chess
Command line chess program written in Ruby
https://github.com/andrewjh271/chess
alphabeta-minimax-search alphabeta-pruning chess game minimax-algorithm regexp rspec ruby
Last synced: 15 days ago
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Command line chess program written in Ruby
- Host: GitHub
- URL: https://github.com/andrewjh271/chess
- Owner: andrewjh271
- Created: 2020-06-18T20:43:40.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2024-04-17T01:07:13.000Z (9 months ago)
- Last Synced: 2024-12-09T09:54:20.930Z (25 days ago)
- Topics: alphabeta-minimax-search, alphabeta-pruning, chess, game, minimax-algorithm, regexp, rspec, ruby
- Language: Ruby
- Homepage: https://andrewjh271.github.io/chess/
- Size: 12.1 MB
- Stars: 6
- Watchers: 2
- Forks: 2
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# Chess
Command line chess program written in Ruby. View on [Replit](https://andrewjh271.github.io/chess/) (But view a faster and more stable version by cloning the repo.)
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[Standard Algebraic Notation](https://en.wikipedia.org/wiki/Algebraic_notation_(chess)) with [PGN](https://en.wikipedia.org/wiki/Portable_Game_Notation) standards is used for both display and input. A few clarifying notes regarding input:
- A move that comes with check or checkmate should have + or #, respectively, appended to the end of the input, but this is not required. The move list will show the symbols regardless.
- O-O and O-O-O are used for castling (the letter, not zero)
- En passant capture is entered as if capturing a pawn that had only moved 1 square (no e.p. at end)
- Disambiguation is required if more than one of the specified piece can move to the target square (e.g. Nbd2 to specify that the Knight on the b-file is meant to move to d2; R1e1 to specify that the Rook on the 1st rank is meant to move to e1)
- Promote a pawn to a Queen, Rook, Bishop, or Knight by appending to the move =Q, =R, =B, or =N, respectively
Enforces the rules of chess, including:
- King cannot move into or ignore check
- Castling is only legal if:
- King is not in check
- Neither piece has moved
- King will not move into check along the path to its destination square
- En passant is only legal immediately following opponent's two-square pawn move
- Checkmate if player to move has no legal moves and their King is in check
- Stalemate if player to move has no legal moves and their King is not in check
- Threefold repetition if position has occured three times, including the following considerations:
- Same player to move
- Same castling rights
- Same en passant rights
- Draw if during the last 50 moves no capture or pawn move has occurred
- Draw if insufficient mating material
User can enter any of the following commands instead of a move:
- **help** - show commands
- **flip** - flip board
- **draw** - offer opponent a draw (the engine will never accept a draw offer)
- **resign** (the engine will never resign)
- **quit** (alias: **exit**)
- **save**
- **tutorial** - shows instructions and examples on inputting moves
A note on display: the pieces are tragically small, but can get a bit larger depending on the font in terminal.
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The chess engine uses a minimax algorithm with alpha beta pruning, but only very modest depths are searched within a reasonable amount of time. A collection of about 4,500 games by [Victor Korchnoi](https://en.wikipedia.org/wiki/Viktor_Korchnoi) is used as the opening database. (Note: The engine depth on Repl.it is by necessity set particularly low.)
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There is an option to play through games from a handful of major chess events over the last half century. When in this mode, there are the following 4 controls:
- **m** - enter next move
- **p** - play all moves at a moderate tempo (every 2 seconds)
- **z** - zoom through moves at a brisk tempo (every 0.2 seconds)
- **q** - quit
-Andrew Hayhurst