Play chess online, free, against the computer

How this chess game works

You play ivory, the computer plays coral, and every rule is in: castling on both sides, en passant, promotion to the piece you choose, check, checkmate and stalemate. Draws are called for insufficient material, the fifty-move rule and repetition. Tap a piece and the legal squares glow. The last move stays highlighted, captured pieces collect in a tray, and a move list in standard notation builds as you go.

Undo takes back your last move and the computer's reply together, so you can try a different idea without restarting. There are three levels. Easy plays fast and makes human-sized mistakes. Normal and Hard look further ahead. The computer thinks in the background, so the board never freezes while it decides.

It runs on a phone with taps, needs no account, and nothing downloads.

A very short history

Chess descends from chaturanga, a game played in India by the sixth century, with pieces that stood for the parts of an army. It travelled to Persia as shatranj and reached Europe through the Islamic world. For centuries the queen shuffled one square at a time. Around the end of the fifteenth century the queen and bishop gained their long-range powers, and the fast, sharp game we play now took shape.

In 1997 IBM's Deep Blue beat world champion Garry Kasparov in a six-game match, a moment that changed how people talk about machines and games. Today a phone engine outplays any human. The computer here is far more modest, which is the point: it's an opponent you can actually beat.

Seven habits that win beginner games

1. Fight for the centre. Pawns and pieces on the middle squares reach more of the board.
2. Develop knights and bishops early. Get them off the back rank before you start chasing anything.
3. Castle in the first dozen moves. It tucks the king away and wakes up a rook.
4. Don't move the same piece twice in the opening unless it wins something.
5. Keep the queen at home for a while. Early queen raids mostly teach the queen to run.
6. Before every move, ask what the computer can now capture. Most beginner losses are a piece left undefended.
7. In the endgame, bring the king out. With fewer pieces on the board it becomes a fighter.

Which level should you pick?

Start on Normal. If you win three games in a row, move to Hard. If you keep losing pieces for nothing, drop to Easy and play slowly: pick a piece, check what it protects, check what attacks it. We haven't given the engine a formal rating, so treat the labels as relative. A strong club player will beat Hard. A beginner will find it plenty.

Three traps every beginner meets

• Fool's mate. After 1.f3 e5 2.g4, black plays Qh4 and it's checkmate in two moves. It only works on someone who opens by weakening their own king.
• Scholar's mate. A quick queen-and-bishop attack on the f7 square: 1.e4 e5 2.Bc4 Nc6 3.Qh5 Nf6?? 4.Qxf7#. Defend f7 and the attack falls apart.
• The back-rank mate. A king boxed in by its own pawns can be mated by a rook or queen arriving on the back row. Make a little breathing room with a pawn move before you need it.

Reading the board and the move list

Files run a to h from left to right and ranks run 1 to 8 from your side upward, so "e4" is the square in the e file on the fourth rank. A piece letter (N for knight, B, R, Q, K) comes first, an x means a capture, a plus means check and a hash means checkmate. The move list in this game follows that notation, which makes it handy for replaying a game later or learning to read published ones.

Endgames worth learning first

The first endgame to master is king and queen against a lone king. Use the queen to shrink the king's area one row at a time, then bring your king over to finish. Next comes king and rook against king. Both are simple once you've seen the pattern, and both turn a won position into a win instead of an accidental stalemate.

Built with a prompt, checked like an engine

This game started as a written brief to an AI coding assistant, and the brief is public on the chess page. The move generator was then tested against the standard reference counts every chess programmer uses: 20 positions after one move, 400 after two, 8,902 after three and 197,281 after four from the starting position. A match on all four is strong evidence the rules are right, because a single mistake in castling or en passant throws the numbers off.