Defend your seven cities against attack from wave after wave of random nuclear missiles. To destroy a missile you must position yourself on a suicidal intercept path and then wait for it to come into your sights. The only chance left then is to press your fire button. The laser power, refreshed from your capital city, is the protection that will save your universe from certain destruction. The higher your level of skill, the more demanding your mission becomes. Missile numbers increase and then split into multi war-heads until the inevitable happens and your capital city is destroyed by the final mushroom. Get straight back into your craft and see if you can hold out any longer in the next game.