The rules of the game are very simple: you need to fill free cells with numbers from 1 to 9 so that in each row, in each column and in each small 3 × 3 square, each number would appear only once.

The game has five difficulty levels:
- beginner (from 33 to 35 open digits),
- easy (from 30 to 32 open digits),
- medium (from 26 to 29 open digits),
- hard (from 23 to 25 open digits),
- extreme (from 20 to 22 open digits).

Autosave works during the game, so you can return to the game if you accidentally closed the application.