Logic grid
Sudoku
Fill 1–9 so every row, column and 3×3 box holds each digit once. Every puzzle is generated fresh on the spot, conflicts highlight instantly, and undo is always one tap away.
Three difficultiesInstant validationUnlimited puzzles
Deal
The grid
Rules
How to play
- The board is a 9×9 grid split into nine 3×3 boxes.
- Fill empty cells with 1–9: each row, column and box must contain every digit exactly once.
- Select a cell and enter digits with the on-screen pad or your keyboard; conflicting digits turn red immediately.
- Difficulty sets the gap count: easy ≈ 40, medium ≈ 46, hard ≈ 52 empty cells — every puzzle has a unique solution.
- Undo steps back; Hint solves one cell (and counts toward the hint tally).
Strategy
Three techniques that carry most puzzles
- Scan by digit. Walk 1 through 9 — if 8 already appears five times, its remaining four boxes often lock straight in.
- Attack the crowded units. Rows, columns or boxes with only one or two empty cells fall first; fewest candidates, easiest wins.
- Mark candidates sparingly. Only pencil marks on cells with exactly two candidates. A board full of notes slows you down more than it helps.
FAQ
About the puzzles
Is this a fixed set of puzzles?
No. Each game generates a fresh solution grid, then carves holes per difficulty with uniqueness checks — effectively endless.
Is every puzzle guaranteed a unique solution?
Yes. The carver verifies uniqueness with a solver as it removes clues, and refills if a second solution appears.
How hard is "hard"?
About 52 empty cells, with patterns that need box/line reduction and naked pairs. Newer players should start on medium.