For the uninitiated, sudoku is a number-based puzzle game that requires using the numbers 1 through 9 to fill a 9x9 grid in a precise manner. There are plenty of sudoku apps out there that supply a puzzle for to you solve and that's it. What most sudoku applications don't have is the ability to teach you to play. ACTSudoku not only gives you a puzzle to play, but can teach the tricks to solving a puzzle that the everyday sudoku player may not know.
ACTSudoku is by far the friendliest sudoku app that I have reviewed to date. Just like every other sudoku application, ACTSudoku gives you the option to choose the difficulty level from easy to hard. Again, just like every other sudoku application, it allows you to suspend the puzzle and finish it at another time. This is where the similarities stop.
The settings page gives you the ability to turn on and off features to your liking. The help section is much superior to any sudoku application I have seen. It gives you sudoku basics as well as solving techniques and ACTSudoku instructions. Inside the solving techniques, they show you different ways of finding numbers to help you solve to puzzle. This is something that I had to spend time learning through trial and error — usually by doing puzzles and see what works and what doesn't. It also comes with support via email so if you're having any trouble with the application, you can easily shoot the developers an email to get your problem solved.
The one thing that brought down the rating for ACTSudoku is that it wasn't very intuitive. It was tough to understand what was going on with the board at the start. I actually had to go back to the first page and read the instructions. It may not sound like a big deal, but I've been playing sudoku for a long time and I'm usually far beyond the "read the manual" stage.
Other than that, ACTSudoku is the most adequate application I have ever seen. With the tips and techniques, it's a good app to start with if you want to learn sudoku. Just make sure you read the instructions.