Graviton 

Graviton is a graphics game. The setting
is 4 solar systems each with a sun and 
4 planets. The object of the game is to 
invade the planets and destroy defenders. 
You have 2000 units of fuel and unlimited
ammunition. It's not all easy sailing as 
there are complications including floating
mines, enemy spaceships, running out of
fuel and GRAVITY... Fun for everyone....