A Python package to play Alice Chess
Project description
Alice Chess
This project allows you to play Alice Chess, a variant of chess.
Installation
The package may be installed through pip
:
$ pip install alicechess
Rules
Here is a description of the concept and rules.
Notable game rules:
- A piece's move must be valid on the board it is on, which means that a piece on Board B can block a check on Board A after teleporting (since the move was valid on Board B, and the move overall was legal because the king is not staying in check). See the above link for a more detailed argument on this.
- Castling: A king and rook may only castle if neither has moved already, the king is not in check, the squares they will move to are vacant on both boards, and the king does not move through check (on Board A) or into check. After the castle, both pieces will teleport to the other board.
- En passant: A pawn may capture another pawn through en passant if your pawn is on Board B and the enemy pawn advances two spaces, teleporting to the space right next to yours on Board B. (This results in a situation that looks like regular en passant.) Note that due to teleporting to the other board after each move, this can only be achieved by a pawn that does not advance two squares on its first move. Also, if there is a piece on Board B where the en passant move would go (i.e., your pawn can already capture a piece normally), then en passant will not take place.
- Fifty move rule: If both players have made 50 moves each where no piece has been captured or no pawn moved, then a player may claim a draw. However, to simplify this case, the game will be automatically ended with a draw (rather than allowing a player to claim a draw). This therefore overshadows the 75-move rule, where a draw is automatically applied after 75 moves by both players with no captures or pawn movements.
- Threefold repetition rule: If a board position appears three times in a game (not necessarily in a row), then a player may claim a draw. However, to simplify this case, the game will be automatically ended with a draw (rather than allowing a player to claim a draw).
How to play
Command Line
To start a game between two human players, you can run the package on the command line:
$ python -m alicechess
A window will come up where the game can be played.
You can also change the players you want to play with by specifying any two of
the builtin players (HumanPlayer
or any of the bots defined in bots.py
):
$ python -m alicechess HumanPlayer RandomPlayer
See python -m alicechess --help
for a list of the possible players.
Script
You can also use a script to run a game. You must initialize a Game
object
with the appropriate players, then call the start_window()
or start()
method.
Here is an example:
from alicechess import Game, HumanPlayer
from alicechess.bots import RandomPlayer
if __name__ == "__main__":
Game(white=HumanPlayer, black=RandomPlayer).start_window()
Note that the class names (not instances) are passed to the Game
constructor.
The start_window()
method will, as implied, start an interactive window where
the game can be played. However, you can also opt to use the start()
method
instead, which will return the first GameState
of the game, and then use
another way to ask the user(s) for input and play the game; for instance, you
could make the game entirely textual with user input provided with the keyboard.
See the API Documentation for more information on GameState
objects,
and check out window.py
for how the windowed game is handled.
In the interactive window, there is a 3 second delay for non-human player moves,
to simulate realism. This can be changed by passing a value for
non_human_player_delay
to the start_window()
method.
To play against your own bot, see the Writing a bot section.
It is also possible for two bots to play against each other.
Writing a bot
The code is factored in a way to make it very easy for you to code your own bots
to play against. Simply extend the Player
class and implement the two abstract
methods for making a move and promoting a pawn. This class (not an instance) can
then be passed into the Game
constructor to start a game. See the
API Documentation for more information.
Here is an example:
from alicechess import Game, HumanPlayer, Player, PromoteType
class MyBot(Player):
"""A very good bot that I wrote."""
def make_move(self, game_state):
for piece in game_state.yield_player_pieces():
for move in piece.yield_moves():
return move
def promote(self, game_state):
return PromoteType.QUEEN
if __name__ == "__main__":
Game(white=HumanPlayer, black=MyBot).start_window()
Credit
Thank you to Artyom Lisitsyn for inspiring me to pursue this project and to Trung Phan for being my chess consultant and answering all my questions on rules and technicalities.
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