Sudoku is a puzzle based on a small number of very simple rules:
Every square has to contain a single number
Only the numbers from 1 through to 9 can be used
Each 3×3 box can only contain each number from 1 to 9 once
Each vertical column can only contain each number from 1 to 9 once
Each horizontal row can only contain each number from 1 to 9 once
Timer
Lives
1
2
3
4
5
6
7
8
9