Chess

Chess is a battle between two armies of sixteen pieces on a board of 64 squares. White moves first, then the players take turns. You win by checkmating the enemy king: attacking it so that it has no way to escape. Play the computer at one of five levels, or pass one phone between two players. Tap a piece to see its moves, then tap a dot, or drag the piece.

How the pieces move

• The king steps one square in any direction. It may never move into check.
• The queen slides any distance in a straight line or along a diagonal.
• The rook slides along ranks and files; the bishop slides along diagonals, so it stays on one colour all game.
• The knight jumps in an L shape, two squares one way and one to the side, and is the only piece that can hop over others.
• Pawns walk straight forward one square, or two from their starting square, but capture one square diagonally forward.

Special rules

Castling moves the king two squares towards a rook, and the rook hops over to the king's other side. It is allowed only if neither piece has moved, the squares between them are empty, and the king is not in check and does not pass through an attacked square. En passant lets a pawn capture an enemy pawn that has just rushed two squares past it, as if it had moved only one. A pawn that reaches the far side is promoted: pick a queen, rook, bishop or knight. If the player to move is not in check but has no legal move, the game is a stalemate and counts as a draw. Games are also drawn when the same position comes up three times, after fifty moves each with no capture or pawn move, or when neither side has enough pieces left to mate.

Tips for beginners

• Fight for the centre early with your e and d pawns, and bring out knights and bishops before the queen.
• Castle in the first ten moves or so to tuck your king away.
• Before every move, ask what your opponent is threatening, and check whether your piece will be safe on its new square.
• Count attackers and defenders before you capture. A knight or bishop is worth about three pawns, a rook five, a queen nine.

The computer levels

Beginner looks only one move ahead and often misses captures, so it is a gentle start. Casual and Club look deeper but still slip up now and then. Strong and Master search many moves ahead and punish loose pieces, so beating them takes real care. Your wins, draws and losses against each level are saved in this browser, and a game in progress is kept, so you can close the tab and carry on later. You get three free take-backs and two free hints per game; a hint shows the move the computer would play.