A free mate-in-one puzzle game. Each round shows a board position and a handful of candidate moves · exactly one delivers checkmate. Pick it to build a streak, miss once and the run ends.

How is the correct answer validated?

A pure function called evaluateMateInOne plays your chosen move on a copy of the board, then enumerates every legal reply for the opposing king. If the king has zero legal escapes and is in check, the move is mate. The validator is the sole oracle · there is no preset "correct" flag to cheat against.

How do I read the moves?

Moves are shown in UCI notation (e.g. e2e4, h1h8). The first two characters are the source square, the last two are the destination. The board is drawn above the choice list with standard Unicode chess pieces.

Does difficulty change the puzzles?

Yes. Higher difficulty widens the set of mate patterns (back-rank, smothered mate, long-range pinning checks) and the labyrinth level ramp grows the choice count from three up to eight plausible decoys drawn from the legal moves in the position.

How does my progress save?

Your high streak is stored locally in your browser.

Chess Mate in One · Deutsch

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