Nice game, I loved the graphics, and the audio fit well. I was a little annoyed by the controls, though. With 50 asteroids on the screen at once, I find it impossible to click on all of them fast enough, let alone click, then press space.
I did manage to win the game, but only after I wrote a quick AutoHotkey script that would click then press space 100 times per second :-) I was able to move my mouse enough to destroy all the asteroids, but just barely. Which is a bit of a shame, the visuals and sounds were great when I destroyed 10 asteroids in a second, but I don't know how accessible that experience is, I certainly can't move my fingers fast enough.
With all of that said, this is still a very impressive first game, and you should be proud of what you were able to do!