The 9x9 board shows a Sudoku solution (i.e., each row, file and each of the nine 3x3 squares contains all nine digits 1,2,3,...,9).
Click the board to randomize the position.
Then click a position which is not at the border. The eight surrounding digits will be rotated clockwise.

In the default variant you win if you can recreate the original position or create a new Sudoku solution.
(You can open a second Sudoxo window with the starting position and use it as a template).

Variant 4: Here you are not given the solution to the Sudoku puzzle, only a scrambled version of it.
Your goal is to create a Sudoku solution (each row, file and each of the nine 3x3 squares must each contain all nine digits 1,2,3,...,9.)

 
Please note that there are three piece sets available.