Could not figure out how to shoot and had to go back to the page to check the controls. Having those directly in the game helps a lot, specially in a downloaded game. I think the bullet trail is a bit too much and distracting and the fact the bullet goes through the Boss without being destroyed or any kind of feeback, makes it hard to tell that you hit the boss and it's kind of underwhelming.
Cute game. Keep doing those. Good job.