Sinistar is a fast paced, very evil looking game. The game basically features you as a ship in space, flying around shooting asteroids to mine crystals used to create Sini-Bombs (the only weapons that work against Sinistar). Sinistar's drones are out mining too ... every crystal they get they take back and construct a new piece of Sinistar. Once Sinistar 'lives' he comes after you. If you don't have enough Sini-Bombs to destroy him, he will annihilate you.
The game featured digitized speech, rare for games at this time - Sinistar would taunt the player saying such phrases as "I Hunger!", "Run, Coward, Run!", "I Live!", and his venerable evil laugh.
Asteroids derived, it was a very advanced game for its time in terms of the depth of gameplay and the graphics.