How to Play Sudoku

1 · Goal

A Sudoku board has 9×9 cells. Use the given digits to infer every empty cell. A complete solution must place 1 through 9 exactly once in each row, each column, and each 3×3 box.

2 · Core Rules

• Each row must contain 1 through 9 with no repeats.
• Each column must contain 1 through 9 with no repeats.
• Each 3×3 box must contain 1 through 9 with no repeats.
• Digits shown at the start cannot be changed; they are your clues.

3 · Controls

Select an empty cell, then press a digit to enter it. Turn on notes mode to record candidate digits instead of a final answer. Conflicts are highlighted when a digit breaks the rules, and Undo rolls back your last step.

4 · Difficulty Levels

Solving Tips

• Start with rows, columns, or boxes that have the fewest empty cells.
• If a digit has only one legal place inside a 3×3 box, place it first.
• Cross-check rows, columns, and boxes together instead of staring at one cell.
• Use notes for uncertain cells, then fill the answer once only one candidate remains.