This is a standalone version of the popular Sudoku game that can be run from a USB key, iPod or a portable hard drive. As it runs off one of these devices, it leaves no traces behind on the computer it is used on.

There are four difficulty levels ranging from easy to virtually impossible. Games are saved when the game is shut down so you can pick up from where you left off, whether this is on the same computer or not.

The empty boxes can be filled with your guess or possible numbers can be added by holding down Shift and using the row of numbers on the top of the keyboard. It is also possible to check the answers supplied so far. Incorrect answers are highlighted in yellow.