Vox

You have to defend the 8 cities of the planet "VOX" from the alien invasion force. You must destroy the alien craft by moving a sight over the screen and firing guided missiles to the sight's location.

There are 40 levels. Each level consists of a set number of alien craft, but an unlimited number of Ammo Saucers and Stunt Planes. To complete a level, you must destroy all the aliens apart from the Ammo Saucers and Stunt Planes.