<title>Antichess Help</title>
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<h1>Antichess Help</h1>

<i>Modified Excerpt from Problem Set 5: Antichess</i>
<h2>The Game: Antichess</h2>

Antichess is a variant of <a
href=http://www.eb.com:180/micro/120/78.html>
chess</a> in which the goal is to lose all of your
pieces.  This section describes the rules of the game.

<h3>The Chessboard</h3>

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 <i>columns</i>.  The eight horizontal lines
of squares are called <i>rows</i>.  The squares are colored black and
white alternately.  The lines of squares of the same color, touching
corner to corner, are called <i>diagonals</i>.  The chessboard is
placed between the players in such a way that the near corner to the
right of each player is white.
<br>
As shown below, the columns are labeled <b>a</b> to
<b>h</b> from left to right. The rows are numbered <b>1</b> to
<b>8</b> from bottom to top.
<br>
<img src="initial-board.gif" alt="Initial Chess Board">

<h3>The Pieces</h3>

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.

<h3>The Moves</h3>

A move is defined by the following rules:
<ol>
<li>White moves first.  The players alternate in making one move at a time until the game is completed.
<li>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.
<li>No piece except the knight may cross a square occupied by another piece.
That is, only the knight may jump over other pieces.
<li>A piece played to a square occupied by an opponent's piece
<i>captures</i> it as part of the same move.  The captured piece is
immediately removed from the board.
<li>A player is <i>forced</i> 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.
</ol>

<br>
Various pieces move in different ways:
<dl>
<dt><b>The King
<br>
<img src="king.gif"></b>
<dd>The  king  moves  to  any adjoining square.
<br>
<img src="valid-moves-king.gif">

<dt><b>The Queen
<br>
<img src="queen.gif"></b>
<dd>The queen moves to any square on the column, row, or the two
diagonals on which it stands (except as limited by rule 3).
<br>
<img src="valid-moves-queen.gif">

<dt><b>The Rook
<br>
<img src="rook.gif"></b>
<dd>The rook  moves to any square (except as limited by rule 3) on the
column or row on which it stands.
<br>
<img src="valid-moves-rook.gif">

<dt><b>The Bishop
<br>
<img src="bishop.gif"></b>
<dd>The bishop moves to any square (except as limited by rule 3) on
the two diagonals on which it stands.
<br>
<img src="valid-moves-bishop.gif">

<dt><b>The Knight
<br>
<img src="knight.gif"></b>
<dd>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.
<br>
<img src="valid-moves-knight.gif">
<br>
The knight may jump over pieces.

<dt><b>The  Pawn
<br>
<img src="pawn.gif"></b>
<dd>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 <i>promotion</i>,
and its effect is immediate and permanent.
<br>
<img src="valid-moves-pawn.gif">
<br>
The pawn at g6 may take the rook.

</dl>
<h3>End of the Game</h3>
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.
<br><br>
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.
