Sudoku
PuzzleFree to playFill in the numbers so that each row and column has no duplicates.
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How to Play
Sudoku is a pure deduction puzzle on a 9×9 grid split into nine 3×3 boxes. Fill every empty cell with a digit from 1 to 9 so that no digit repeats in any row, any column, or any box.
The board opens with a set of pre-filled "givens" that cannot be changed. Tap an empty cell to select it, then tap a digit on the on-screen pad to place it. Every entry is checked against the hidden solution straight away: a correct digit locks in, while a wrong one still lands on the board but increments your mistake counter and plays a reject sound. Because wrong entries stay visible, the mistake count is your feedback loop — a rising count means your assumption chain is broken, not that the puzzle is unfair.
The puzzle is complete when all 81 cells are filled. There is no timer and no penalty beyond the mistake tally, so the whole game is about how few wrong assumptions you need.
Controls
- Tap an empty cell - Select it
- Tap a digit 1-9 on the on-screen pad - Place that digit
- Tap a filled cell you entered - Select and overwrite it
- New Game button - Generate a fresh puzzle
- Sound button - Mute or unmute the feedback tones
Tips & Tricks
- 1Sweep box by box rather than row by row: each box constrains only nine cells, so contradictions surface fastest there
- 2For any digit, check where it can still go in a box — if only one cell qualifies, that cell is solved
- 3When two cells in the same unit share exactly the same two candidates, that pair claims both digits and you can eliminate them from every other cell in the unit
- 4Start with whichever digit already appears most often on the board; it has the fewest open slots
- 5Keep the mistake counter at zero for as long as possible — a wrong entry you forget will poison later deductions
- 6If you are stuck, re-scan rows and columns for a digit placed eight times; the ninth position is forced
- 7Work the crowded regions first: a box with six givens is far easier than one with two
Frequently Asked Questions
Can I choose a difficulty level?
No. Each New Game generates a fresh puzzle at a single difficulty, so challenge varies naturally from board to board.
Is there a pencil-mark or notes mode?
No. This version has no candidate notes, so you track possibilities in your head or on paper.
Do I need to be good at maths?
Not at all. The digits are symbols — the puzzle is pure logic with no arithmetic involved.
What happens if I enter a wrong number?
It stays on the board but your mistake counter increases by one and a reject sound plays, so you get immediate confirmation that a deduction was wrong.
Can I erase a cell I filled?
Yes. Select any non-given cell and place a different digit over it; the givens themselves are locked.
Is there a time limit?
No timer at all. Take as long as you like — nothing is scored against the clock.
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