I got a score of 150 by holding down A and clicking extremely fast. My fingers are tired now.
While this is definitely a game, it really needs more variety. The shrinking planet as health bar is good, but it just generally needs more...anything.
I found the spinning speed of the planet to be too slow, either that or the enemy speed is too fast, since sometimes it just doesn't give you enough time to spin around and aim at the incoming enemies. I think there are some things in this game that could be worked on to improve it.
All in all a great effort :)