Great presentation, and an intresting mechanic. The critique i could give is that, the differing effects from the powerups don't really change the gameplay up too much, rather; like the mirrored controls, it just hinders or supprts the abillity to kill the enemies. If you were to make a newer version, i would reccomend adding some extra spice to the powerups. In addition the enemies have a tendency to get stuck on objects, and are a bit annoying to go look for after you killed all the other enemies.
But that was what i had to critique. The gameplay is great and the presentation is top-notch, posibly the best looking jam game iv'e seen so far.