This is a command line ruby implementation of chess. It has a simple AI and can be played human vs human, human vs AI, or AI vs AI.
You will need Ruby installed on your system.
Download the code, navigate to the main directory, and run bundle install. Then run chess.rb with your ruby interpreter (i.e. type ruby chess.rb in the terminal). You will be prompted to select the type of game you want to play.
Move your cursor with the wasd keys. To move a piece, bring the cursor to its position and press enter to select it. Then move the cursor to another position and presss enter again to move it. To deselect a selected piece, press enter with the cursor over any invalid move position.
Valid move positions are highlighed in yellow.
To quit the game, press q when it is your turn. When viewing an AI vs AI game, press ctrl+c to abort the program.
This game was built from scratch with Ruby. It uses the colorize gem to color the board on the command line, and the io-console gem to enable use of $stdin.getch.
To determine valid moves, pieces include one or more of the "stepable," "straightable," or "diagonalable" modules. Shared functionality between the straightable and diagonalable modules is factored out into a separate "slideable" module.
The board uses the null object pattern for empty squares, allowing it to call piece methods on all squares, even if they are empty. For example, calling valid_move? on an empty square will return false rather than raise an error.
The board has a custom dup method, which returns a deep copy of the board. This is used to test whether a move will leave a player in check. It is also used by the AI to test possible moves.
This game has a simple AI implementation, with the following basic logic:
- If a move that checkmates the opponent is available, make it.
- Otherwise, if a move that puts the opponent is check is available, make it.
- Otherwise, if a move that takes an opposing piece is available, make it.
- Otherwise, make a random move.
At each step, if there is more than one option available, one is chosen at random.
- En Passant
- Saving and loading games
- Improve AI