This Touchscreen Hand-held Sudoku is different from all the others because obviously it is a touchscreen game which is a rare thing. One of its great features is the auto-save that saves battery by turning off when no one is using it. There are 4 levels of difficulty and there are more than 800 puzzles to make. If you are a pro, try playing with a timer for more challenge, for newbies there are game hints to make the game easier to play. It is available at ThinkGeek for $20.