The the manual of the game: Save the Earth from the diabolical Trillians. They have set up Attack Bases which launch Kamikaze Satellites and Trillian Fighters. You must stop them! Every Satellite that gets by you, will explode on Earth and drain your energy sources. Every time your Space Destroyer is hit by Trillian Fighter fire, more energy is lost. To regain energy, you must seek out a Trillian Attack Base and destroy it. It is very important to keep your energy level high. If you lose it all, the Trillians will have a celebration as the Earth dies screaming.