NullDoku-9

How to play

1. Fill the grid so every row, column, and 3×3 box contains the numbers 1 through 9, with no repeats.
2. Tap an empty cell to select it, then tap a number below the grid (or type it on your keyboard) to fill it in.
3. Bold numbers are given and can't be changed. Cells you fill in show in the accent color.
4. A wrong number turns red so you can spot it. Filling in every cell correctly finishes the puzzle.
5. Pick Easy, Medium, or Hard at the top, or hit "New game" to start over.