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Chess for the console, with a focus on computer AI.


Clone or download zip. To play a regular game load the Game.rb file (e.g.ruby game.rb). To run a comparison of the 2 computer AI's load the game_test.rb file with a command line arg for how many test games should be played (e.g.ruby game_test.rb 10).


A regular game let's you choose any combination of computer and human players (white computer will be the stronger AI, black the weaker). The Game class is designed as an api that allows both types of players to interface with it.

The human player inputs his moves using proper chess co-ords (e.g e2, e4) which are then converted into the array co-ords

The computer player uses a custom made AI to compete.

A special game mode, game_test especially created for comparing computer ai. It plays the amount of games specified in the first ARGV, and outputs the result totals. (Games have a capped length (75 moves) in this mode to ensure results are produced in a reasonable time)

The Piece class uses polymorphic methods and inheritance with Slideable and Stepable inherritting from Piece and the individual types of pieces inheritting from them in turn.

Computer AI

The better AI gives a score to each possible move accounting for piece mobility and pieces captured, minus the score of opponents best response. For mobility extra weight is given to the central squares with less weight given to the side columns. Piece values are updated in their respective classes based on game situation. (Currently only implemented for Pawns in last 2 row, with others planned).

Rules not yet implemented

en passent and castling board position repeats 3 times, and 50 move rule (no capture or pawn moved).


Create a number of AI strengths and let the player choose the computer difficulty.