Gamers tired of fast-paced action titles and their cutesy saccharine counterparts should take heart. There are some alternatives for Sony's PlayStation Portable (PSP) that are not filled with big explosions, gunfire or a Looney Tunes character rip-off. A few titles for the PSP have none of these video game staples. One such example is Go! Sudoku, a digital version of the popular numbers puzzle that has taken the world by storm. Go! Sudoku, created by Liverpool Studios, is similar to the puzzles you will find in the South China Morning Post and other newspapers. The digital version of the game, however, has settings that can be customised, allowing players to select the level of difficulty. Puzzle sleuths can choose from easy, mild, difficult and the extremely hard - or fiendish. The 'style' option allows players to choose an accompanying atmosphere for game play, categorised into the four elements of fire, water, air and earth. There are also presets for background music and animations. The game features a number of soothing New Age music tracks that play in the background. It also offers a range of colourful screensaver backgrounds that do not distract players from concentrating on solving the puzzle. The Pass Sudoku game allows between two and four players to take turns solving the same puzzle by passing around the PSP. After players have taken their turn, a time indicator shows how long each took, which is then added to their overall playing time. In the wireless mode, gamers can compete in a time trial with other PSP players. Game play is fairly simple: the left and right shoulder buttons cycle through the numbers one to nine. The 'x' button puts in the number you think is correct, while the 'circle' button places smaller numbers in the square, which are your guesses. The 'square' button deletes. With hundreds of puzzles for you to solve, Go! Sudoku will keep you entertained for quite some time. It slips into that interesting niche occupied by Tetris, Pacman and other exciting time-passing games.