John's Sudoku is one of the most comprehensive Sudoku game systems. It randomly creates puzzles for six difficulty levels. You may never meet the same puzzle. But you can do the same one via user defined puzzle. Or you can define your own puzzle via Sudoku Book. You can also share the same puzzle with your friends via the importing/exporting function of this system. The followings are the summary of the function:
1. Randomly creates puzzle for six difficulty levels.
2. User can define his/her own puzzle, e.g. from Sudoku Book.
3. Check the status and highlight the error.
4. Easy to see the working cells with the most advanced highlighting function.
5. Auto-pencil the selected cell.
6. Undo/Redo function.
7. Auto-pencil (or auto-erase) all the cells with one tap.
8. Revert to the last clean state via 'Eliminate error input'.
9. Resolve the puzzle .
10. Import/export your puzzle to share with friends.
11. Reset to the original puzzle.
12. Game is auto-saved. You only need
to tap Resume when you return to the app.