Sudoku classic.

Classic sudoku game for your iPhone and iPad. Features: - Four difficulty levels (easy, normal, hard, very hard). - Tutorial with several techniques (from beginner to advanced) for solving the game. - Unlimited undo and redo. - Game saving. - Notes. - Auto noting empty squares. - Auto updating notes. - Square coloring with two colors for advanced techniques. - Error checking (manual and automatic). - Share the game with a friend via whatsApp, email, etc...