The app allows manual input of a sudoku game; uses "-", "|", "X" and "O" to stand for removing possibilities by row, column, section and pair, therefore a user can easily get the reason.
Five game levels can meet the need of all players. The game level can be set in Option.
The free version can illustrate solution for 10 times, but click the ad bar below can recharge it.
The link for the app is:
https://itunes.apple.com/us/app/sudoku-tutor-free/id646030534?mt=8
some screenshots show the app features:
