A logic puzzle, not a sum

Fill the 9×9 so every row, column, and 3×3 box holds 1 through 9 once. No arithmetic. The given digits are the only clues you need.

How to play

Some cells are given. Select an empty cell, then tap a number. Use notes to pencil candidates. Auto-check (on by default) flags a digit that doesn’t belong in the finished puzzle. Three mistakes end the round.

Tips

• Start with rows, columns, or boxes that already hold five or more digits. The remaining cells are often naked singles.
• When a digit appears twice across a band of three boxes, the third copy has only one box left — scan the nine cells there.
• Pencil marks are cheaper than guesses. Fill notes, then look for hidden singles: a digit that can live in only one cell of a unit.