The game takes place in a maze and the screen layout stays the same for every level, although the colours and the graphics do change to add a bit of variety. The object of the game is to guide your craft around the maze and blast everything that moves. When all the aliens have been destroyed the level ends.

Each level contains a number of different nasties who each have their own strengths. The bug looking creature which is known as "Henry" is easy to dispose of but the "JCB" is indestructible from the front so you have to have to shoot at it from behind. On later levels mines get laid around the screen.

There are power-ups to collect to assist you in the destruction of aliens. The best one is the "Immediate Zap" which destroys all aliens on the screen instantly. Other pick ups include bombs, shields and small zaps which you can collect and use as and when you need to.