I really enjoyed the art and music! I'm jamming out to the music right now!
However, I think you made one mistake (albeit an easy to fix one if you choose to do so): The hit detection. I know some people have commented about it already, so instead of critiquing it harshly, let me give you a tip about hit detection. ALWAYS make enemy hitboxes SMALLER than their sprite. Often times 2-3 pixels in on each side works wonders. This is because the player will often times be making close calls, and with how the human mind works and such, many hits will seem quite unfair, even if they are realistic. As a game developer, always remember to develop the game with the user in mind. Don't be afraid of feedback, even if it's very harsh. :)
I really enjoyed your game, and I'd love love love to see a full verison, with the problems fixed and many more levels :D
~ Adam "PixelDough" Worrell, from the Duck Jam team