# Antichess Help

Modified Excerpt from Problem Set 5: Antichess

## The Game: Antichess

Antichess is a variant of chess in which the goal is to lose all of your pieces. This section describes the rules of the game.

### The Chessboard

Antichess is played between two opponents by moving pieces on a square board. The board is composed of 64 equal squares. The eight vertical lines of squares are called columns. The eight horizontal lines of squares are called rows. The squares are colored black and white alternately. The lines of squares of the same color, touching corner to corner, are called diagonals. The chessboard is placed between the players in such a way that the near corner to the right of each player is white.
As shown below, the columns are labeled a to h from left to right. The rows are numbered 1 to 8 from bottom to top.

### The Pieces

At the beginning of the game, one player (``White'') has 16 white pieces, and the other (``Black'') has 16 black pieces. Each player has one King (at e1 for White, e8 for Black), one Queen (at d1), two bishops (at c1 and f1), two kinghts (at b1 and g1), two rooks (at a1 and h1), and eight pawns (row 2). The initial position of the pieces on the chessboard is given above.

### The Moves

A move is defined by the following rules:

1. White moves first. The players alternate in making one move at a time until the game is completed.
2. A move is the transfer by a player of one of his pieces from one square to another square, which is either vacant or occupied by an opponent's piece.
3. No piece except the knight may cross a square occupied by another piece. That is, only the knight may jump over other pieces.
4. A piece played to a square occupied by an opponent's piece captures it as part of the same move. The captured piece is immediately removed from the board.
5. A player is forced to capture an opponent's piece whenever possible. If a player can take several of the opponent's pieces, she is free to choose which piece to take.

Various pieces move in different ways:

The King
  The king moves to any adjoining square.
The Queen
  The queen moves to any square on the column, row, or the two diagonals on which it stands (except as limited by rule 3).
The Rook
  The rook moves to any square (except as limited by rule 3) on the column or row on which it stands.
The Bishop
  The bishop moves to any square (except as limited by rule 3) on the two diagonals on which it stands.
The Knight
  The knight's move is composed of two different steps; first, it makes one step of one single square along its row or column, and then, still moving away from the square of departure, one step of one single square on a diagonal. It does not matter if the square of the first step is occupied.
  The knight may jump over pieces.
The Pawn
  The pawn is the only piece whose moving regulations are different from its capturing regulations. A pawn may only advance forward. It may move one vacant square along the same column. In addition, for its first move it may also move two vacant squares along the same column. When capturing, it advances one square along either of the diagonals on which it stands. On reaching the last row, a pawn must immediately be exchanged, as part of the same move, for a queen of the same color as the pawn. This exchange is called promotion, and its effect is immediate and permanent.
  The pawn at g6 may take the rook.

### End of the Game

The first player who has no legal move wins the game. This occurs when a player has no piece left, or when all pieces are blocked from making a legal move. Unlike real chess, the king has no special significance in this game. The game continues even if the king is captured.
We shall play antichess with time restrictions, as is often the case in chess games. Each player is allocated a fixed amount of time to make all the moves, say, 5 minutes. There is a clock for each player that is set to 5 minutes at the start of the game. If it is player A's turn to move, A's clock will count down until the move is made. While it is B's turn to move, A's clock is suspended, and B's clock runs down. If a player's clock runs down to zero while the game is in progress, the player loses. This ensures that the game is over in less than 10 minutes, because by then at least one of the clocks would have run down to zero.