It is super impressive that you pull all this together alone in 72 hours. The visuals, the sounds, the mood, are all very much at the top. That's why this is probably the most frustrating experience I've had in LD50.
***Un-dodgeable attacks are almost always a bad idea***, unless you are going for the whole "it can't be defeated" narrative. The lighting attack is practically undodgeable, and I don't see a reason for that. You can make it only hits you for 2 ticks if you run, but that's the best you are gonna get. If you stay out of the outer ring, the boss seems to just give up on the more reliable lighting and start spamming fire, which is easily dodgeable. If the lighting is a close range deter, it would probably make more sense to just do an AOE around the boss rather than auto aim hit scan.
What I'm saying here is, if you want the player to stay away from the boss (which IS the meta btw), convey the idea clearly. I was trying to make the orb easier to connect by standing just far enough from the boss to not get burned alive, and whether the boss decide to do the lighting attack or the fire attack seems to be random. So I assumed that you have to simply just out damage him by avoiding the avoidable fire and tanking the lighting, and leave the rest to chance, which is clearly not the intended gameplay here.
This is frustrating not because the combat is mediocre, but because the other aspects are splendidly done that it really throws you off. I'm still giving it a high score for the work put into the visual and level design and actually programming a working boss, but I saw potential in it I don't see in some other games and it is so unfortunate the boss fight lacks proper polish.