Rules of chess
The game of chess is played between two players on a 64-square chessboard, with squares of alternating light and dark colors. The board is placed so that a light-colored square is in the corner nearest each player's right hand. Each player controls sixteen pieces: a king, a queen, two rooks or castles, two bishops, two knights, and 8 pawns. At the beginning of the game, the pieces are arranged as shown in the diagram to the left: the rooks are the pieces in the corners, next to them are the knights, then the bishops, and queen and king in the center, behind the 8 pawns.
The player controlling the white pieces moves first, then the players alternate moves. A "move" is any one of:
- Moving a single piece of your own color from the square it is currently on to an empty square, according to that piece's method of movement (for the moving methods, see the articles about the individual pieces);
- Moving a piece to a square occupied by an opposing piece and removing the enemy piece (called a capture);
- Castling (see castling);
- Promotion (sometimes called "queening"; see pawn); or
- En passant capture (see pawn).
Check, Checkmate
A player's king is never captured. When a player makes a move that threatens the opposing king with capture, the king is said to be in check, and the player with the move is required to immediately eliminate the threat by one of three means:
- Move the king to a square not threatened;
- Capture the threatening piece; or
- Place a piece between the king and the threatening piece.
A player may never leave his king in check at the end of his move.
In informal games, it is customary to announce "check" when making a move that puts the opponent's king in check. In formal competitions, this is not only unnecessary but may be considered annoying or distracting.
If a player's king is placed in check, and there is no legal move that player can make to escape check, then the king is said to be checkmated, the game ends, and that player loses. The diagram to the right shows a typical checkmate position. The white king is under attack by the black queen; every square to which the king could move is also attacked; and he cannot capture the queen, because he would then be attacked by the rook.
Draws
The game ends in a draw on one of these conditions:
- The player to move is not in check but has no legal move (this is called a stalemate, and such a position is shown in the diagram to the left);
- There is no possibility for either player to mate the opponent, because there are insufficient pieces remaining;
- By agreement of the players.
Either player may claim a draw by indicating that one of these conditions exists:
- Fifty moves have been played by each player without a piece being captured or a pawn moved.
- The same board position has been repeated three times, with the same player to move and all pieces having the same rights to move (including such things as the right to castle or capture en passant). In particular, if a player is able to check the opposing king continually (perpetual check) and he indicates his intention to do so, the game is considered a draw.
Tournament games are played under time constraints. If a player oversteps his allotted time, he loses automatically. Various tournament rules have been devised to prevent players from playing on in drawn positions, with no practical chances of winning on the board, intending merely to win when their opponent runs out of time. If a player believes his opponent is attempting to win a drawn position on time, he may appeal to a tournament official. The tournament official then either declares the game to be drawn, or penalizes the player who made the appeal and orders the game to continue.
Games of chess in formal competition are recorded as they are played for later analysis. Algebraic chess notation is presently used for this, though some older books still use descriptive chess notation.