I really like the visuals and the generel gameplay idea.
Here are some things I think could be improved:
-Music and sound:
Even though the background sound sets a great mood in the beginning, I think some more aggressiv music during the actual gameplay would support the game feel. I also would add an explosion sound when the asteroids get destroyed.
I feel the game could be faster and more tight. Maybe decrease the asteroids health and increase the spawn amount? I think there is to much idle time every now and then. Maybe also increase the start rotation speed?
These are just some random thoughts I got while playing. Overall I really like the game.