Really easily exploitable. Just stand on the bottom area and shoot and jump, and you are basically invincible.
Also, sometimes I would turn into a blue bat after getting hit by one. When that happens, I usually cant move for atleast 3 seconds or so sometimes compromising the game.
Evolving into creatures actually makes the game harder, so it seems to be a better strategy to avoid the pellets enemies drop entirely.
Finally, I have a recommendation.
It is pretty hard to spam click to shoot without a mouse. Could you make a key like K which hands normally rest on a key you can press to shoot as well.
I enjoyed the game, though. It was a pretty nice premise, and I had a good time trying to get the highest score possible. I got to about 10.5k. I hope the problems can be fixed.
Anyway, I would give the game a mid-low 4 stars because it was fun, but not very interesting to play after about 30 minutes. It just became repetitive.