Liberator

Liberator is rather like a reverse Missile Command. Your guns are at the four corners of the screen. In the center of the screen is a planet that is rotating. You must move a cursor onto the planet's cities and press your fire button to destroy them. The nearest gun will then fire. Destroy all the cities to clear the level. The planet is not helpless, however, as they send up missiles and ships to attack your guns. You can shoot these down, as well, or use a shield to temporarily protect your gun. You have unlimited firepower but shields are limited.