nice game, I liked the level design lots of fun.... I reached (so far) the point with 2 flying bosses, and they kill me so quickly (to be honest I struggled with just the one!) Might come back to it though I suspect just to get killed again over and over, loved the way the world opens up with each new power up, and destroying the brown walls was a nice touch (even if is not clear those walls should hurt them if you touch them otherwise).
I know you have used existing assets but you've done it nicely! Good job overall!