Classic Sudoku Guide

What you are doing

Fill the grid so digits 1 through 9 appear once in every row, column, and box. The useful move is the one forced by current constraints, not a guess that happens to fit locally.

Controls

Select an empty cell, then choose a digit using the on-screen keypad or supported keyboard input.

Practical notes

• Scan one digit across all boxes before switching digits.
• Use notes for candidates when the interface provides them.
• If a contradiction appears, revisit the last uncertain entry rather than changing several cells.

Before you start

Difficulty levels, hints, and mistake limits are build-specific and not promised here.