Sudoku Mini is a great version of the classic puzzle but I'm not quite sure why it's called mini, apart from the obvious - it's on a mobile - reference.
Because Sudoku Mini is packed with all the features that you want from your Sudoku puzzles. There are various levels of difficulty, variable grid sizes and a built-in puzzle generator meaning you have literally billions of games to play.
The grids vary between 4x4, 6x6 and 9x9 plus there's an undo function if you make any false move. There isn't, however, a pencil mode which I really like in the mobile versions of Sudoku games I play nowadays.
Far better than an undo button. The puzzles are colourful and clear and it'll keep you entertained for as long as your journey to and from work lasts.