How to Play
Sudoku
Sudoku is a number-placement puzzle on a 9×9 grid. Fill
every empty square so that each row, each
column and each of the nine 3×3 boxes
contains the digits 1 to 9 exactly once.
The clues you start with are fixed. Every puzzle here is generated with
exactly one solution, so you never have to guess blindly — there is
always a logical next step.
Difficulty
Each level caps how hard the reasoning can get, so a puzzle is never
tougher than the label promises. The Technique readout
shows the hardest step the grid in front of you actually needs.
- Easy — around 40 clues, and every step is a single candidate.
- Medium — fewer clues; at worst you need locked candidates.
- Hard — at worst you need naked or hidden pairs, triples and quads.
- Expert — minimal clues, and reasoning beyond the standard patterns.
Controls
- ClickSelect a square
- 1–9Enter a digit (again to clear it)
- ←↑↓→Move the selection
- ⌫Erase the square
- NToggle pencil marks
- UUndo
- HReveal one square
Tips
- Scan for a digit that has only one legal home left in a row, column or box.
- Use pencil marks to park the options for a square before committing.
- Best times are only kept for grids solved with no mistakes and no hints.