Snake is a also a game that is available on most Nokia mobile phones (all of those since 1997), although the newer ones have Snake II. A purist would argue Snake II simply removes the fun simplicity of the original thereby destroying it.

The premise is this: you control a snake (a line of pixels) who has to eat some sort of fruit (represented by more pixels) and the more you eat, the longer you become making the game more and more difficult.

There are multiple levels of difficulty and on the higher ones, you travel faster but this is compensated for by the fact that you recieve more points for each apple you get.

You die if you hit yourself or a wall, and the keys are as follows:

2 = up
8 = down
4 = left
6 = right

Of course, more advanced users (not me) can use 1, 3, 7 and 9 to move diagonally, but this gets pretty complicated.

The game is stunningly addicitve, helped by the addition of a 'high score' screen which prompts the user to keep on playing until he/she beats his old record. The game's success relies on the fact that it was firstly the best game available when Nokias were released and so it was the only thing available, but also by the fact it followed the rules that all great games follow.

It was simple, the screen wasn't cluttered and there was an incentive to keep playing.

Pure genius.