ACT Sudoku is an expansive sudoku gaming application that allows you to save games, choose difficulty levels and even make notes on which numbers you've used so far. It comes with basic instructions, techniques and game directions to help even the most confused novice.
The game starts you out with the choice of difficulty, settings and the option to read through instructions prior to gaming. In-game, players can actually make notes to what they've used in a row or column by tapping once in the pop-up grid that appears when you tap a block. Tapping a number in the grid twice places the number in the block.
Users can either abandon or save their games, and tips can be given whenever you'd like. For a free application, ACT Sudoku is surprisingly versatile.