Sudoku 401 app for iPhone and iPad

If you want to improve your Sudoku skills, Sudoku 401 will help you learn and play.

Sudoku 401 is a Sudoku game, a generator, a solver, and a teacher/tutor.

First, it is a serious Sudoku game.

- Puzzle generator for unlimited play. You will never see the same game twice.
- Clean and simple game board, so you can focus on the playing instead of being distracted by colors and/or shapes.
- Ability to enter the game manually, copy from newspaper, books, or other software.
- Tap on a clue to highlight potential locations for the number. Tap again to go back to normal viewing.
- Automatic or manual pencilmarks, which can be switched during the game play with one tap.
- Automatically saves the game when you leave, ability to continue when you come back.
- Option to use either symmetrically or non-symmetrical Sudoku boards.
- Option to show error.

Even more, it teaches you the logic and techniques of Sudoku, with its multi-step teaching system. All of the techniques are human logic, not computer brutal force.

- Difficulty level is defined by the techniques used, not by number of clues.
- Beginner: Full House, Hidden Single and Naked Single.
- Moderate: Hidden and Naked Pair, Locked Candidates.
- Challenging: Hidden and Naked Triple and Quad, X-Wing.
- Difficult: Swordfish, Jellyfish, XY-Wing and Finned X-Wing.
- Expert: Squirmbag, Finned Swordfish and Jellyfish (that also includes Fishy Cycle, Sashimi Fish and Turbot Fish), XYZ-Wing and WXYZ-Wing.
- Extreme: ALS-XZ (Almost locked set) and Finned Squirmbag.

Check out our screenshots to see how the teaching works.