Your comet streaks forward on its own through a scrolling asteroid field. Drag up to flare your tail wide and sweep up drifting stardust for bonus points, or drag down to thin it out so it fits cleanly through narrow gaps between asteroids — clip one with your tail and you lose a life. It's a constant trade-off between greed and precision, and both the gaps and the field's speed tighten the longer you survive.
Flare your tail for stardust, thin it for asteroid gaps.