If you've wondered what all the fuss was about over placing numbers on a grid, Go! Sudoku will introduce to you the best little game since Solitaire. Where Solitaire sometimes feels more like exercise for your mouse hand, Go! Sudoku offers a nice level of mental stimulation that falls somewhere between games of chance and the Sunday crossword puzzle.

For Sudoku fans who struggle to keep paper copies of their game neat, having a nice, clean Game Grid is the only design feature necessary. Those of us who like flashy interface will not see much to cheer about, but what Go! Sudoku may lack in style, it makes up for in substance. The Game Grid features a preset background that can be switched out with a little work to feature a photo of your choosing. Between creating a folder to hold photos, resizing and reformatting photos, casual gamers may just decide to use the standard background images. At least the presets are nice looking... Why there isn't some way to use photos from the Photos folder on your PSP as background images, I don't know. And, why there isn't some option to customize music and select from the library of songs included on your PSP, I also don't know. What we're left with is the fact that Go! Sudoku stresses gameplay over design, but luckily, the gameplay is quite strong.

At first, I found the Sudoku concept disarmingly simple. Place the numbers 1 through 9 on a Game Grid so that no number is repeated in a straight line or in any 3x3 grid. The easiest comparison would be to a crossword puzzle, when you start looking at multiple lines to determine which letter is missing from a word you can't guess. The fact that Sudoku puzzles contain only numbers means there isn't external logic in any sequence. It's not as if you get a hint as to what particular number sequence is present in any part of the puzzle. The internal logic is what makes Go! Sudoku. The other comparison I make is to Minesweeper or any derivative of that game. As you would look at a 3x3 "mines" grid and try to infer the content of mystery spaces, both by what you see and what you don't see, Go! Sudoku is all about context.

Learning the game is easy, because there's a good tutorial. If you want to teach friends or just turn them onto the game, you can share a sequence of simple puzzles that give someone a taste of the action. The different modes in Go! Sudoku include Solo, which offers over 1,000 puzzles! At least 200 more are available for download from the publisher's site, either using a PSP or your PC. Much like the background images, you'll have to manually create a folder in which to store the additional games, which may be beyond some gamers. Rest assured that if you never download a single puzzle, there are 1,000 zingers included on the UMD to tide you over. All but the most fanatic Sudoku'er will have plenty to get them through.

Wireless play for between two to four players can be a lot of fun if you happen to know other fans. The Battle Mode is a turf war, with each player working in an assigned color and trying to place as many numbers as possible. Once the Grid is full, the player with the most color on the board is the winner. Versus Mode is similar, but here the goal is to complete a Game Grid before the other players, regardless of who picks the most numbers. In both cases, guessing or consistently choosing incorrectly results in demerits and can lose you the battle. Even in the Solo game, Go! Sudoku is anything but guesswork. Sure, there are only nine number combinations, but guessing is a slippery slope. A few bad outcomes and you've set the whole puzzle on a spin. If you aren't up to the more challenging puzzle, there are some good helper features and a wealth of puzzles rated Easy or Mild.

Calling a puzzle Easy doesn't mean it's any smaller, or that the rules change. What can be changed is a feature that fills in some "candidates" automatically, allowing you to see all options at once. When you choose a number, the candidate list changes for surrounding cells, which makes it easy to narrow down choices. I wish there had been more history and talk of strategy in the game. Assuming that we know everything limits Go! Sudoku from being able to reach out to novices and brand new players. Using Wikipedia, it's possible to learn a bunch about Sudoku, but shouldn't we be able to get this through the game?

At least in Solo play, Go! Sudoku allows you to take time and look around at all options, even test out candidates along the way to build your own "work in progress" Game Grid. Each match is timed for performance. More than half of the 1,000 games are either rated as Easy (440) or Mild (320), but that still leaves over two hundred rated as Hard or "Fiendish." And that's not includng newer games that can be downloaded.

Unlike games where control schemes may thwart some gamers, Go! Sudoku is so simple a complete novice can pick it up and figure out controls. Moving around the Game Grid is done with the D-pad, and the shoulder buttons cycle through numbers. Placing candidates is handled by [O], and the other buttons place or delete candidates, and take back a previous move if necessary. As puzzles get harder, placing candidates is more important, but not practical outside of Solo play. The multiplayer options are nice, and I wish there had been more thought and time invested in making the download options for new Game Grids or music or backgrounds more transparent. Really, I'd rather not have to pop out my memory card or do a lot of USB wrangling between my PSP and computer... Isn't that why we have wireless connections in the first place?

If round after round of Solitaire is wearing you down, or you just don't want to be a complete sheep and take up Poker, Go! Sudoku may bring salvation. There is a subtle lure in the game that I can't say I'm immune to on the basis of being able to jump in and play at any time. The pick-up/put-down quality of Go! Sudoku makes it a good companion on the morning commute, a rainy weekend day, or just a spare moment when you'd like to put up your feet and still work the gray matter. But for a few technical shortcomings, Go! Sudoku does a great job emulating the paper-and-pencil version of this popular Asian import. That said, Sudoku isn't the kind of simple game that lets you while away hours without a lot of focus, which its true fans appreciate. For them, this is a gem.