Honestly, at first i didnt know what was going on, i didnt know you could attack or what i was meant to do, other then avoid the red circles,,, I had to read these comments to figure out what to do, but as benhen said, i just went to the boss and clicked, and it died.

Fun idea, and I liked the bosses sprite, however as Taylor said, it was a little too frustrating trying to land bullets

I like the idea here and the consistent style is cool. It was very hard to both move away from bullets and face the enemy at the same time. 
Nice effort.