Sudoku X4 offers classic Sudoku puzzles and three variations that we think you'll love. Our irregular Sudokus have odd-shaped groups which require a slightly different perspective as you work through them. X variations on classic and irregular Sudokus complete the selection. In addition to the usual Sudoku rules, these X-Sudokus have a fourth restriction in the diagonals, which must also contain the digits 1-9. Not really harder, just interesting variations on the simpler Sudoku puzzle types.

Our Sudokus have 6 levels of difficulty, from absolute beginner to really, really hard. For newbies or aficionados who just want to relax, there are puzzles that require only simple techniques. At the other end of the scale, we have puzzles with Franken Fish, XY-Wing and other extreme patterns that will challenge even the most advanced puzzlers.

We hope you enjoy using Sudoku X4 as much as we enjoyed creating it!