Chess

Play a full game of chess in your browser. You are White against the computer, or choose two players. Tap a piece to see its legal moves, then tap a highlighted square. All the rules are built in: castling, en passant, promotion, check, checkmate and stalemate.

How to play

1. Tap one of your pieces; dots show its legal moves.
2. Tap a dot to move. Pawns promote to a queen automatically.
3. The game ends in checkmate (the king is attacked and cannot escape) or stalemate (no legal move, not in check), which is a draw.

Piece values

The computer uses these values (slightly adjusted for central squares) and looks 1, 2 or 3 moves ahead with minimax search.

Chess and math

Chess is full of counting: there are 20 possible first moves for White and 400 possible positions after one move each. The number of possible games is so large (the Shannon number, about 10¹²⁰) that no computer can search them all, so programs estimate positions instead.

Chess quiz: 10 questions

Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.

Frequently asked questions

Can I play chess against the computer for free?

Yes, at three levels, with no sign-up.

Are all the rules included?

Yes: castling, en passant, promotion (to a queen), check, checkmate and stalemate.

Can two people play?

Yes. Choose Two players and take turns on one device.

How strong is the hard level?

It searches three moves ahead with alpha-beta pruning, enough to punish loose pieces; strong players will beat it.

Can I take back a move?

Yes. Undo takes back your move and the computer's reply.

Sources

• FIDE Laws of Chess
• Shannon (1950), Programming a Computer for Playing Chess

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