Levels, the higher level you are, the harder it would be, and if you want add a background story.Also add more features to the meteorites
...That would actually be really awesome. Finding mining bases or something on asteroids and wrecks to continue the story. The game does get harder the higher your score. The asteroids increase in number until it's basically a solid wall. Badly implemented though if it wasn't quickly obvious. I like the idea of features to the asteroids too, I had an idea at the start to include a laser to break up asteroids, but i'll save it for another game. Thanks for the feedback!