Chess vs Computer

How to play chess against the computer

Chess is a two-player game on an 8x8 board. Each side starts with sixteen pieces: eight pawns, two rooks, two knights, two bishops, a queen and a king. White moves first, and you take turns until one king is trapped. On this page you tap a piece, tap one of the dots that appear to move it, or simply drag it. The dots show only legal moves, so you can never make a mistake with the rules, only with the position.

How the pieces move

• Pawn: one square forward, or two from its starting square. It captures one square diagonally forward and is promoted when it reaches the far edge. You choose a queen, rook, bishop or knight.
• Knight: an L-shape, two squares one way and one to the side. It is the only piece that jumps over others.
• Bishop: any distance diagonally, so it stays on one colour of square for the whole game.
• Rook: any distance along a rank or file.
• Queen: rook and bishop combined.
• King: one square in any direction, and never onto an attacked square.

The special rules

Castling moves the king two squares toward a rook, and the rook hops to the 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 cross or land on an attacked square. In this game, move the king two squares and the rook follows. En passant lets a pawn capture an enemy pawn that has just advanced two squares and landed beside it, but only on the very next move.

How a game ends

Checkmate wins: the king is attacked and has no escape, no block and no capture of the attacker. Stalemate is a draw, which happens when the side to move has no legal move but is not in check. A draw also comes from threefold repetition, from fifty moves by each side without a capture or pawn move, or when no one has enough material left to mate, such as king against king and a single bishop. You can resign or offer a draw at any time. The computer usually accepts when it is clearly worse or the game has dragged on level, and otherwise mostly says no.

Choosing a difficulty

Beginner looks one move ahead and sometimes plays a careless one on purpose, so it hangs pieces like a new player would. Casual sees a move or two and still blunders now and then. Club calculates three plies and plays an opening book. Strong, Expert and Master use deeper alpha-beta search with check extensions, quiescence search and no deliberate errors; Master gets about 1.5 seconds a move. Everything runs in a background thread on your own device, so the board never freezes.

Five habits that win games at club level

1. Move each minor piece once in the opening, fight for the centre with pawns on e4 or d4, and castle by move ten.
2. Before every move, ask what the opponent's last move threatens. Most lost games end with an unanswered threat.
3. Check, capture, threat: list the forcing moves first. Forks, pins and discovered attacks decide most games below master level.
4. Trade when you are ahead in material and avoid trades when you are behind.
5. In endgames, activate your king and push passed pawns. A rook behind a passed pawn is worth far more than the pawn alone.

Try the daily puzzle for tactics practice. Each one is a forced mate in one or two moves and was checked by exhaustive search, so there is exactly one key idea. Your streak counts consecutive days.

Frequently asked questions