Sudoku Challenge for Android
There is no support for hints nor any tutorial of any sort. Hints just destroys the challenge of the game (you can thank me later for not including this) and detailed tutorials can already be found everywhere on the net. This game does not include help of any kind, that would make puzzles easier to solve. It does not allow breaking the rules of the game though, so in a way that is a kind of required minimal assistance. There is no rule checking done for candidate marks.
This app focuses completely on keeping the challenge just the way it is when played with pen and paper, but adding the convenience of storing all games and progress for as long as desired and the ability to correct mistakes easily. It also has a manual edit mode so a puzzle found on paper can be added and stored in the collection. The puzzle generator also adds an unlimited supply of new and valid (a puzzle with exactly one possible solution) puzzles whenever needed.