Hyper Sudoku: 250 Hard Four Box Sudoku Puzzles: 12 (Windoku)

Hyper Sudoku: 250 Medium to Hard Four Box Sudoku Puzzles: 15 (Windoku)

Hyper Sudoku: 250 Hard to Very Four Box Sudoku Puzzles: 16 (Windoku)

Hyper Sudoku: 250 Easy to Medium Four Box Sudoku Puzzles: 14 (Windoku)

Windoku Sudoku Puzzles: 204 Medium to Hard Puzzles