Five machines.
One king.
Full chess — castling, en passant, promotion, the fifty-move rule, the lot — against five machines on a ladder, or against another person in a conversation where you can watch them think.
Play it now ▸ — solo against the machine for the highscore board, or 1 on 1 with somebody on the network.
Real chess against five opponents, from one that hangs its queen to one that does not lapse. The board records which of them you have beaten.
Where the board came from
Chess reached Europe from India by way of Persia and the Arab world, and the version played today settled in the late fifteenth century when the queen and bishop were given their modern range. Almost everything about the game that makes it worth six centuries of study dates from that one change: it turned a slow positional game into a sharp one.
The machine on the other side of this board is the other half of the story. Chess has been the standard test of game-playing programs since Shannon described how one might work in 1950, and a browser can now run a search that would have been a research project in the 1990s. The five here are that search, deliberately turned down to five different strengths.
How the ladder works
- Pick a machine and a colour. Teal moves first, amber second, or let it decide.
- Play the game out. Click a piece and then its square, drag it, or use the arrow keys and Enter — the board is fully playable without a mouse.
- Beat a machine and it goes on the highscore board. Only the hardest one you have beaten counts, so a win against SENTINEL replaces a win against DRONE rather than adding to it.
- A draw is worth two fifths of a win, and a loss is worth nothing. Nothing is deducted for losing — the ladder only ever records what you have actually done.
- Every finished game is replayed on the server before it is recorded, including a sample of the machine’s own moves. A game where the engine was made to walk into mate does not verify, whatever the move list says.
Climbing the ladder
The bottom two rungs make deliberate mistakes and will hang material if you give them the chance; the way through them is simply to take what is offered and not to hang anything back. PROBE looks one move ahead, DRONE sees the capture in front of it and misses the one it is walking into.
SENTINEL upward is where it becomes real chess. From there the machine searches deeply enough that tactics alone will not do it, and a plan is worth more than a trick — control the centre, develop everything before attacking, and do not open a file you cannot use.
OVERMIND does not lapse. It plays no deliberately weak moves at all, and the only way past it is a genuinely good game.
Questions
Is this real chess?
Yes — every rule, including castling both sides, en passant, under-promotion, stalemate, threefold repetition, the fifty-move rule and insufficient material. The engine is the same code that checks a submitted game afterwards, so the rules on your screen and the rules on the server cannot drift apart.
Can I play another person?
Yes. Choose chess and search for an opponent and you queue on chess as your topic; the next person who wants the same game lands in a conversation with you, and the board opens between you with a clock running. You are on video unless you turn the camera off.
Do games against people go on the highscore board?
No. Only solo runs against the machine are ranked, because only those can be checked. A game played out on somebody else’s computer goes on your win–loss record instead.
Do I need an account?
To record a run or to play a person, yes. The board runs in any modern browser and there is nothing to download.
The rest of the arcade
Pong, Tetris, Oware, Draughts and Snake. All of them play the same two ways: against a machine or against a person.