It had to happen some time or other. It was a matter of inevitability that someone, somewhere would invent a handy oriental puzzle game you didn't need to lug around in a book or newspaper. Now those clever Japanese have done it again by finding a way of compressing and miniaturising the genius that is Sudoku so it fits on your humble mobile telephone.

Now the colour screen of your telephone is no longer just for pictures of flowers, the space shuttle, or the grainy image of the person who's calling. Now you can happily be driven mad by the high art of numerology, wherever you are. Hurrah.

This handily downloadable mobile version of Sudoku comes with an in-built tutor - a type of on-board checking device - so you can happily keep track of your progress as you go. Alternatively, to go seriously hardcore, turn the tutor mode off and compete with the best in cyberspace for the right to have your score added to the online high score list.

With multiple levels of difficulty and a seemingly endless number of quizzes to choose from, this innovative use of your telephone is guaranteed to have you thinking of a number. In sum, it all adds up. Wonderful.