Good concept and great start.
On my first run, it felt a tiny bit unfair because I had no way to predict direction of incoming asteroids, and I thought I had no way to speed up or improve my odds...
On my second run, I realized I could move the little asteroid and it was slightly faster than the big one, so it was a much better experience. Had a bit of a QWOP vibe to it.
(I admit, sometimes I play a game without reading the instructions carefully.)