My two nitpicks are: 1) Although the game is super juicy and feels great, the big chunky particles are occluding and make the screen very busy; I often lose track of where I am. 2) Not necessarily bad thing (because I don't know the answer), but I wonder how readable this game would be to someone who is colorblind.
With the nitpicks out of the way-- The amount of polish and style on this game is through the roof. I like how the entire game flows from one thing to another. I like the transitions between fights. I like how everything feels alive despite it all just being squares with rounded corners. And above all I love the simple but clever upgrade system and how it affects the enemies of the current color you are primarily fighting. I'm glad I was able to finish it, I had a good time! Great work!