Sudoku FAQ
Common questions about rules, difficulty levels, scoring, and strategies.
What is Sudoku?
A number puzzle on a 9×9 grid. Fill every row, column, and 3×3 box with the digits 1–9 — each digit used exactly once per row, column, and box. No math required; it's pure logic.
How do you play Sudoku?
The puzzle starts with some cells pre-filled. Click an empty cell, then press a number key (1–9) to fill it. Use hints if you're stuck, or undo if you make a mistake.
What are the Sudoku difficulty levels?
Easy (35 cells removed), Medium (45), Hard (50), Expert (55), Master (60). More removed cells means harder — fewer starting clues force deeper logical deduction.
What happens when you make a mistake?
A red highlight marks the conflict and your mistake counter increments. Three mistakes ends the game. The board tracks mistakes so you can learn from errors.
How do you solve an Expert or Master Sudoku?
Use elimination chains, naked pairs, and X-wing patterns. Start with rows, columns, or boxes that have the most filled cells, and look for cells where only one digit can fit.
What is the hint button?
Hint reveals one correct digit in the selected empty cell. Easy allows 5 hints; Expert allows 1; Master allows none.
Can I undo a move?
Yes — press Z or tap the Undo button to revert your last entry.
How is the score calculated?
Score increases with time remaining when you complete the puzzle and decreases with each mistake. Fewer mistakes and faster completion equals a higher score.