How Hansu works
Move first, find out immediately
Each puzzle is a real position from a real game where one side has a forced winning sequence. You play a move on the board. If it is not the winning move, the board does not change, so you try again from the same position. If it is the winning move, the opponent's reply plays automatically and you continue to the next move. There is no answer key to peek at before you try; the feedback is what teaches you.
Where the puzzles come from
All 5,400 puzzles are drawn from the public Lichess puzzle database (released under CC0, public domain), filtered to sequences with strong community verification (popularity and play count) and a short, learnable length. We did not write new puzzles or alter the moves.
How we checked them
Before a puzzle shipped, we replayed its full move sequence, one move at a time, through our own chess rules engine (the same one behind our openings reference, Cheotsu) and confirmed every move was legal in that exact position, including castling, en passant, and promotion. Any sequence that failed was dropped rather than shipped with a guess.
What we don't show
We don't show win rates or popularity rankings for individual puzzles, since we don't have a trustworthy source for that per puzzle, and made-up numbers would be worse than none. We also don't rate how good your move was beyond right or wrong for the puzzle's solution.