Wow! This is something special. This is a creative idea, and you knocked it out of the park. And it feels amazingly polished for 30 days. I didn't beat it, but I want to come back to it when I have more time.
Each of the bosses feels unique, especially since they seem to get some different attack patterns when played in a different order. And everything just feels good. My only gripe is that some of the attacks seemed to stick around longer than intended. I had some red fish still on the screen when the next boss showed up :P