The art looks cute and lovely, music is nice, animations are cool.
But here's some (hopefully constructive) criticism: The locked camera makes it difficult to see where enemies are coming from. There's no indication of building health most of the time (health bar just doesn't show up), and because of that I have no idea if the healing buildings are actually doing anything. The difficulty is trivial up to the point where the enemies start instantly killing your buildings when they get close, at which point it's just a random chance to lose a building once in a while, because the turrets don't rotate fast enough to hit them if they're facing the wrong way. An option to hold down the upgrade button would be nice, I must have hit "E" several thousand times in a single playthrough. There's a bug where you can place a building onto a grassy tile, if something on it has just been destroyed. The manual shooting feels weak and pointless after the first couple of waves, the area is large enough that you can't really respond to any threats yourself and it seems to only work at very close range. And some kind of ending would have been nice (even just a fade to black and "you survived 222 waves!" or something).