Chess
Every rule of chess, and an opponent that never looks at your reply
About Chess
The rule set is complete, and the fiddly parts prove it. Castling checks that the king is not in check now, will not be where it lands, and does not cross an attacked square on the way. En passant appears as a legal capture on an empty square for exactly one move, then vanishes. Threefold repetition folds castling rights and the en passant file into the position it hashes, so a board that merely looks familiar is not counted twice.
The opponent is a different matter and worth being straight about. It scores each of its legal moves once, sorts them, and plays one from the top group. There is no search underneath: it never asks what you would do in answer. That makes the three levels behave like three opponents rather than one at three volumes — Easy is close to random, Normal grabs whatever is loose and drifts toward the middle, Hard plays sharply and greedily for exactly one move at a time.
Two people can share the board instead. Nothing is timed, and the strip above the board carries three things: whose turn it is, the move number, and who is ahead on material.
What is different about this version
Most browser chess bundles a search engine and hides it. This one has no search at all, so the levels change the scoring rather than the depth. Easy is essentially a shuffle. Normal adds a mild capture bias, a pull toward the centre and a bonus for castling, then picks at random from its best third. Hard weights a capture at ten times the value of what it takes, adds eighty points to any move that gives check, awards a pawn eight hundred and fifty for reaching the last rank, and subtracts only a third of a piece's own value for stepping onto a defended square. It also chooses at random among everything within thirty points of its best move, so no line can be memorised against it. No clock, no move list, no undo.
How to play Chess
- Pick your opponent from the pause sheet: the AI at one of three levels, or another person sharing the board.
- You have White and move first. The board never flips, so in two-player mode Black plays from the far side.
- Select a piece and its legal squares appear as dots, captures as rings. The last move stays tinted.
- Castle by moving the king two squares toward the rook; the rook slides across on its own.
- Take en passant by moving your pawn diagonally onto the square the enemy pawn skipped.
- A pawn reaching the last rank becomes a queen at once. There is no piece to choose.
- Checkmate ends it; stalemate, repetition, insufficient material and the fifty-move rule end it as a draw.
Controls
| Desktop | Click a piece and then its destination, or drive a square cursor with the arrow keys and confirm with Enter; Escape or P pauses. |
|---|---|
| Phone or tablet | Tap a piece to light up its legal squares, then tap the one you want. |
| Players | One or two people on the same device. Nothing here plays over the internet. |
Strategy
The one thing the opponent cannot do is see your reply, and every plan against it starts there. On Hard a capture is worth ten times what it takes, while landing on a square you defend costs it only a third of the value of the piece it moved. Those two numbers do not balance. Leave a pawn hanging that two of your pieces guard, and the queen will often come and take it — a queen for a pawn. It works most cleanly around move eight or ten, once a couple of defenders are aimed at the same square.
Its other weakness is that check is worth a flat eighty points whether or not the check achieves anything. It will shove a queen forward to give a pointless one, and each of those is a free tempo if you can block or capture with a developing move. Let it come; do not chase it. Every retreat you force is a move spent on a piece that was never coordinated with anything.
Otherwise play ordinary chess, because ordinary chess is what beats it. Endgames are where it collapses completely: with few pieces left, its centralisation bonus drags the king toward the middle of the board while you are pushing a pawn past it, and it walks into queening races it cannot count. Against a person none of this applies and the board reverts to the game you already know.
Mistakes that cost you the game
- Leaving a piece loose because the engine looks weak. Captures are the one thing its scoring is sharp about.
- Playing for a slow squeeze. It has no plan to punish, so a quiet game just hands it more free captures.
- Assuming a position reached three times is a draw. Losing the right to castle in between makes it a different position.
- Promoting expecting a knight or a rook. It is always a queen, which in a few endings turns a win into stalemate.
- Treating Easy as preparation for Normal. Easy rewards the habits Hard punishes.
Tips
- Develop the knights first and castle inside ten moves — that is the window where the AI's development bonus applies and it briefly plays sensibly.
- Bait with a defended pawn, not a defended piece. A pawn is cheap enough that the trade pays even when declined.
- Trade queens when you are ahead. Without one its moves turn aimless.
- Treat a sudden flip in the material readout as a warning that something was hanging.
- Check the dots before committing on a phone. A mistap on a crowded rank is how a good position usually goes wrong.
Questions about Chess
Which special moves are actually implemented?
Castling on both wings with full legality checks, en passant, and promotion — always to a queen.
How does the AI decide on a move?
It scores every legal move for captures, checks, pawn advances and centralisation, then plays one at random from its top group. It does not look ahead.
Which draws does it recognise?
Stalemate, threefold repetition, insufficient material including same-coloured bishops, and the fifty-move rule.
Can I take a move back?
No undo and no move history, so a blunder stands.
Is there any time pressure?
None. A position can sit untouched and be picked up later in the same tab.
Does it work from the keyboard alone?
Yes — the arrow keys move a cursor around the board and Enter selects.
Does it cost anything?
No. Chess is free to play, runs in your browser, and needs no download, install or account.
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