Very impressive! This felt like a fully fledged game one would find on the Nintendo E-shop. The color swapping mechanic is super, and then you've got some really nice enemy variety! Then all the upgrades feel great, and the animations and sound effects, just fantastic stuff! It all really makes you feel like a penguin in a musical war.
Unfortunately got OOM and game crashed on wave 29, but that's what I get for playing the web build.