Gravitar expanded upon the basic concept of Lunar Lander while adding a series of increasingly devious level designs, ground-based turrets, alien attackers and boss-like reactor levels, in addition to color vector graphics. The control scheme and cabinet design are essentially the same as Asteroids and Space Duel, though Gravitar didn’t sell as well, at least partially because of its brutal level of difficulty. Black Widow was released as a conversion kit for Gravitar, and in fact used the same PCB with updated ROM chips.