From the depths of space come Earth's deadliest adversaries: the Vogons. Destroy successive waves of these barbaric creatures as they hurtle towards you in convoys. Each convoy consists of a number of Vogons which snake their way down from the top of the screen, changing direction if they hit an asteroid and splitting into two if hit in the middle. As the game progresses, additional hazards are introduced. Chargers dive-bomb your shuttle craft and Crushers bounce across the ionosphere. The Crawlers create 'warp vectors' from asteroids in their path. If the Vogons come into contact with any of these they are immediately transported to the bottom of the screen. Asteroids (including the warp vectors) can be destroyed by two shots, the second shot causing debris to fall towards your craft. An extra life is awarded at 5,000 points.