Stardust is basically Asteroids, but with a lot of gameplay modifications. There are 30 standard levels split into 5 worlds. The 6 levels a world is made of can be completed in any order. However, you must fight an end-of-level bad guy once you have finished the 6th level of a world. While each level has the standard disintegrating rocks to destroy, all but 2 of them have extra bad guys, with a range of attack patterns.