Gravitrex

Gravitar was a vector graphic arcade game that took some of the elements of Asteroids (the controls and free flight abilities of the player's['] ship[s]) but made them more restrictive by placing players inside a series of planets. Players had to skim surfaces of the planets and destroy all the bunkers therein, as well as beam up fuel cells to maintain their fuel level(s) and avoiding or destroying saucers that would also appear. The game did not do very well commercially and would only be ported to the Atari 2600 a few years later (although it has reappeared on some modern day compilations since).