I'm amazed at how much technical knowledge of PICO-8 this must have required. Seriously, great job.
If I had to provide one piece of constructive criticism it would be that if the middle of an enemy sprite is visible, then the whole sprite is drawn even if it's in front of a corner that should obscure part of it, but I'm not sure how possible that would be to fix, it depends how you're utilizing the sprite system. But if you can't fix it don't even sweat it, it's phenomenal already.