This game is definitely visual proof that the rtp can make some good maps, and for atmospheric environments if used correctly. I'm hazarding a guess it's meant to be reminiscent of WW1's trenches, with Emilia trying to find her brother, but also escape alive after an attack. Unfortunately that's all there really is to it, and I agree with Sith that the game could have used more exposition, maybe with the notes on the desks being written by the soldiers there with thoughts of why they're there and what's going on. Something to further build the world and immerse the player fully into Emilia's shoes.
I can only assume the green bubble status effect means the player is poisoned, but the game never provides anything to heal that damage. As a result I would start resetting the game any fight it happened, and quickly enough just began avoiding fights all together. Especially once I noticed she wasn't gaining XP from fights, so there's literally no gain to fighting except maybe hoping to get back some amount of the ammo you used. There's also a box in one of the rooms in the upper right area where the box just says "weapons gained". I didn't have anything new in my inventory, and I'm guessing it was a bit of filler that was missed.
I'm hoping you update this once the Jam is over, since I'd like to see what you fully intended this to be.