Learn Sudoku
Five short lessons that take you from the rules to spotting moves like a pro.
The rules
Three rules. That's it. Hover a cell to see what counts as a row, column, and box.
How to play
Click a cell, type a number. We'll walk you through a 4×4 puzzle step by step.
Using notes
When you're not sure, jot down candidates. Press N to toggle Notes mode.
Naked Single
A cell where every other digit is already used in its row, column, or box.
Hidden Single
A digit that can only fit in one spot within a row, column, or box.