This was a lot of fun, such an athletic little slime! The shooting animation is hilarious, and even before full flight was unlocked it was funny to just keep holding Jump, bounce and fly up ladders. The bosses were really easy, but didn't seem to out of place with the light tone. The grey enemies were a nice surprise, normally I'd be irritated by camouflage like that.
Some minor bugs: Going back through the Grand Agonizer battle I fell off the world (though I'm not sure exactly how this happened). Generally fading everything, not just the background, near the biome exits means that it's possible to hit an invisible enemy there. The power icon shouldn't overlap one of the health hearts.