**One Sudoku** offers Kendoku puzzles in sizes 3x3 to 6x6. Four difficulties are available for the larger variants. The small sizes 3x3 and 4x4, suitable for beginners, are available in *Easy* and *Advanced*.

The variants differ in the arithmetic operations (division is required in *Expert* and *Challenging*) and the allowed order for subtractions (*Easy*: only from large to small, for example 6 - 4 - 3, from *Challenging* onwards other orders can be considered). Starting from the difficulty level *Challenging*, groups can also contain the same number more than once.