Clubroom

You won

by checkmate

Settings

a StuStudios game

The back room of a chess club, one lamp, and a tournament set. Play the regulars, a friend on the same screen, a box of puzzles, or set up any position and let the club's engine look at it.

Moving

Drag a piece, or click it and then click where it goes.
You can premove while the other side is thinking. Click anywhere to cancel the premove.
Right-drag draws an arrow and right-click marks a square. Hold Shift for green and Ctrl for red. A left click clears them.
Drag the table or use the middle mouse button to walk round the board. Scroll to lean in.
On a touch screen, drag a piece or tap it and then its square, drag the table to walk round the board, and spread two fingers to lean in.
← → step through the moves, Home End go to the start or end, F turns the board, V changes the view, D swaps the table for the diagram and back, M mutes, Esc cancels.

How it works

Each piece is a turned profile, revolved like wood on a lathe. The move-list icons are drawn from the same profiles. The knight is the one piece a lathe can't make, so it is a carved silhouette with rounded edges.

The diagram is the same set laid flat, the way a chess book prints a position: the dark squares engraved, the coordinates in the margin, a caption saying whose move it is. Each piece is its lathe profile with a line wherever the lathe cut an edge. In review the annotator's glyph is set on the square the move went to. It needs no graphics card, so it is the board wherever the 3D table cannot start.

The rules engine is checked by perft against the six standard reference positions, which together are over sixteen million positions that must come out exactly right. That covers castling through check, en passant pins and underpromotion. Every puzzle in the box is checked too. A mate is proved by exhaustive search, so each move you have to find is the only one that mates as fast; on the last move, any mate counts. Every other puzzle is the engine's judgement, looking at least twelve half-moves ahead: each move you have to find beats every alternative by at least two pawns, and no alternative still wins clearly.

The day's puzzle is one from the box, the same for everyone on the date in Taipei. The Lamp's notes are not from the box: they are positions from your own reviewed games, and a move counts there when the Lamp judges it good, giving away under 5% of your winning chance. That is the Lamp's judgement at the moment you play, not a proof like the box's.

The club ratings are the regulars' own estimate, not FIDE ratings. The weaker players aren't a strong engine with noise added. They look a few moves deep, choose among the moves they like, and sometimes overlook something, which is how people lose pieces too.

Are you sure?