This is another entry this mvm that is really unique. I love the simplicity, yet abstract art. I could tell what was environmental, what were enemies, etc. There was nothing art wise that stuck out. I loved how the water splashing looked and the sense of buoyancy.
I do have a nitpick about the controls being only arrows keys and movement mechanics, abilities being Z,X,C, and A. I'm a "WASD" guy so this setup always makes it a little more difficult for me, but as long as the layout makes sense and isn't all over the place, its not something that affect score.
I guess my main critique, and its a really picky one, is that as a plain square, its not intuitive which direction I'm facing. I've used a square before and received the same feedback. It felt obvious to me as the developer, but I made the assumption it would be the same way for everyone else. Thankfully, your character can shoot so, constantly shooting helped in that regard. My game didn't have that so I can see where it would have been counted against me.
And as Jeff said, it would have been nice to have the floaters line up more, but I think my entry also has the same kind of issue.
Overall, this is a great and really cool entry. I definitely think it was well executed and visually impressive.