Has potential, but right now, it's boring
Game is simple enough, but indeed, it is experimental-just didn't feel like a complete game. I primarily give ratings based on gameplay, and shooting at only asteroids, no matter how pretty the effects are, can't really hold anyone's interest for long. Still, if you were just testing some code, this could be the base for an even cooler SHMUP.
I felt that it took longer than it should for the action to really pick up, though. (around 500000 points or so).
There are many things you could do with this if you ever come back to it in order to make it a good vertical shooter. Make enemies with different patterns, separate stages, an upgrade system of some sort. Pretty sure you know what else goes in.