Chances are, you’re fully aware that the number-placement logic game Sudoku is massively popular. But if you’ve been in a cave the past few years and need evidence, look no further than the 18 (and counting) versions of Sudoku apps available in the iTunes App Store, ranging in price from 59p to £5.99.

If you’re a fan of Sudoku, which do you buy? Unfortunately, the current state of the App Store doesn’t allow for demo versions of software, leaving you to take a wild guess based on a short description and a few screenshots. But we’re here to help: I tested every iPhone Sudoku app and picked out those worthy of your iPhone’s screen.

Each of the three versions that made it through my screening process, and are covered here, satisfy the following requirements:
* Uses a standard 9-by-9-cell grid of numbers with nine square (3-by-3-cell) regions. (Some Sudoku variants break the standard 9-by-9 grid into non-square geometric areas, or use colors or images instead of numbers.)
* Includes puzzles with only a single solution.
* Provides a way to note (or ³pencil in²) the possible values for each square as you solve a puzzle. (These markings are often called notations.)
* Offers good usability: easy-to-use input methods, clear controls, and readable graphics. (For example, a couple Sudoku apps that didn’t make the cut satisfied most criteria, but their methods for making notations obscured other parts of the puzzle.)
* Includes puzzles for multiple skill levels.

Unfortunately, none of the better Sudoku games available for the iPhone and iPod touch exclusively use symmetrical puzzles - those in which the pre-filled boxes (called givens) in opposing regions mirror each other.

Although not technically a requirement, many purists don’t consider non-symmetrical puzzles to be ³true² Sudoku. I tend to agree, but I didn't hold a lack symmetry against the candidates. However, I’ve noted in the summaries below if an app uses symmetrical puzzles.

If you’ve never played Sudoku before, I recommend checking out Wikipedia’s page on the game; these reviews assume you know the basics.

EA's Sudoku

Electronic Arts (EA) first released a Sudoku game for the 5th-generation iPod back in 2006. The company has updated that game for the iPhone, and except for the fact that you enter numbers using the iPhone’s touchscreen instead of an iPod’s Click Wheel, the gameplay is almost exactly the same.
Which is good on two fronts: the original game was pretty good, and the new input method makes the game much more enjoyable.

Like the iPod version, EA’s Sudoku for iPhone offers gorgeous graphics - along with the same lengthy launch and screen-transition times - and 10,000 unique games spanning five difficulty levels (Easy, Normal, Hard, Very Hard, and Insane). You can choose the difficulty level before each game, although you must solve a Hard puzzle to unlock Very Hard, and solve a Very Hard to unlock Insane.

Similar to Big Bang Sudoku, you input numbers using a row of buttons across the bottom of the screen: 1 through 9, along with a separate button to toggle between solving and notating. However, like Sudoku Vol. 1, above, you tap a cell once to highlight it, and then you can tap multiple notations for that cell; I prefer this approach, as it requires less tapping the way I solve puzzles.

On the other hand, I did have a few minor complaints about the controls themselves. In addition to the buttons being on the small side, the notation/solve button displays a pen in notation mode and a notation icon in solve mode, which seems backwards to me. The number buttons also appear and disappear as you work with the puzzle. For example, when you solve a cell, the controls disappear and don’t appear again until you tap on an unsolved cell. Although I understand the ³contextual² theory behind this approach, I found it slowed down gameplay as I had to wait for the controls to fade in each time I tapped on an unsolved cell.

When solving puzzles, an error-checking option can identify incorrect cell values, and a hint feature solves the ³easiest² unsolved cell (or corrects the easiest mistake).

As with Sudoku Vol. 1, tapping on a solved or given cell highlights all other cells containing that solved or given number. Another nifty feature is Auto-Fill, which automatically fills the notations for all empty cells.
Although useful as an aid in solving a puzzle, it’s also a convenient way to speed up a game: with all notations filled in, you can jump ahead to using logic to actually solve the puzzle. And with the iPhone version of the game, you can activate Auto-Fill by shaking the iPhone vigorously!

One other great feature offered by EA Sudoku is Newspaper mode, which lets you manually enter and play puzzles from a newspaper, Sudoku book, or online game. If you’re feeling adventurous, you can even use this mode to create your own Sudoku puzzles; a validation feature will tell you if your homemade puzzle works.

EA has included detailed, text-based help that explains the rules of the game as well as all options. You also get statistics on your progress, as well as a scoring system that awards points for solving puzzles, reducing the points earned when you use hints and the error-checking feature. You can toggle music and sound effects on and off separately, as well as adjust the overall audio volume within the game.

EA Sudoku’s games are non-symmetrical at higher difficulty levels.

Currently not available on the UK App Store.

## OUR VERDICT

EA's offering is visually appealing and its 10,000 puzzles should keep you busy for a long, long time.