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Game
Tutor suggestions
Arrows appear here on your turn: green is the engine's top choice, red and grey are the runners-up.
Moves
Game report
Analyzing…
How the tutor works
The engine behind the board is JavaScript inside this page: no chess library, no downloaded engine, no server. It searches a few moves ahead (deeper at higher strength levels) and scores positions by material and piece placement. Its move generator was validated against the standard perft test suite, including the classic castling and en-passant trap positions.
Every tutor explanation is derived from facts the engine can verify on the board (a capture, a check, a piece left undefended) and from its own numbers. The score shown next to each suggestion is in pawns, from your point of view.
The post-game report replays your game, compares every move you made against the engine's preferred move, and grades the difference: inaccuracy, mistake, or blunder. The accuracy percentage is this page's own formula on the engine's own scale, so it is not comparable to lichess or chess.com numbers. Once a game is completely decided, the remaining moves are marked but not graded.