Fun yet frustrating.
It was a treat to play even though it lagged a bit for me.
I loved the various enemies with different flight patterns.
The level up and down was a thoughtful addition.
The backgrounds and music created a pleasant atmosphere.
Having said that, the game is almost impossible.
It's hard enough to reach the first boss, let alone beat him. And don't even think about reaching the other bosses.
I don't see why you need 9 MB for a game like this. You should bring it down to 5 MB at least.
Good job on this. I hope to see more soon.