Very nice, Good Job on getting that into <64kb.
The Eye in the Sky gives a real ominous feeling to it all, works beautifully with the simple Textures on those Cubes, really had my fantasy going wild thinking up possible Lore reasons for me shooting the Orbs.
I would have liked a more varied leveldesign instead of constantly generating 1 Cube wide Pillars in vision Range, if you'd just create them out of the Fogfloor and not floating, and gave them Varying widths, I'd envision myself in some kind of Skyline facing off against cosmic horror Aliens or something, but thats not really needed to have Fun.
Had a Problem with the Pink Fog, when flying beneath it, it obstructs the whole Screen with a opaque Pink, making it next to impossible to find your way back out again, should either not be possible to go below, only tint the Screen instead of being Opaque then, or kill the Player or something probably.
If this had the above mentioned Things, some mainmenu/gameover/victory condition, a bit of enemy variety, and some of them also flying around shooting, insted of only explosive orbs, and a retro high octane Soundtrack, this would be a really really impressive Submission.
Keep in mind, I think its still great regardless of that tho.
But the Rings shot by the Orbs seemed to not extend smoothly, I don't think its an issue with framerate, as everything else felt super smooth, so maybe its intended? Just felt odd a little.