To start a new game you can either click anywhere in the square below or press a key (for the first game you will need to use the mouse, this gives the game the focus). Once the game is started you can control the worm using the following keys :
Up : j
Down : n
Left : a
Right : s
Pause : p
To unpause simply press any key. The case is important so please make sure you haven't got caps lock on. The idea is to go around the screen picking up the numbers (by running over them), that number of cells are then added to your worm. You die by either running into the edge of the screen or running into your own tail. The high score table is shown on the main screen.

Additions.