How to play +
Fill every row, column and 3 × 3 box with the numbers 1–9, once each. The dark numbers are fixed clues.
Notes hold your possible numbers. Placing a number clears that note from its row, column and box. Check compares your entries with the solution; it never fills an answer.
Erase cell clears the selected cell, including all its notes. Undo last restores your previous edit anywhere on the board, including an erase.
Keyboard: arrows move; 1–9 enter; N toggles notes; Delete clears; Ctrl/Cmd + Z undoes.
Difficulty is based on solving techniques. Easy uses singles, Medium adds hidden singles, and Hard needs locked candidates or pairs. No guessing is required by our solver.
