Sudoku

Classic Sudoku — fill the 9×9 grid so every row, every column, and every 3×3 box contains 1-9. Each new round serves a fresh puzzle from a curated bank of five per difficulty, so you don't see the same board twice in a sitting.

Tap a cell, then tap a digit (or press a number key). Toggle Notes mode (or press N) to pencil in candidates as small marks; placing a digit on a cell auto-clears matching notes from its row, column, and 3×3 box. Undo steps back through your last actions; Erase clears the selected cell. Conflicting cells turn red. Score is your elapsed time; lower is better.