3 things:
1. The art and colors are great, and animations and effects are very well made and work nicely with the gameplay (consistency of style and the right stuff being emphasized vs. not emphasized, etc.). You clearly had an artistic vision you were carrying out, which makes it enjoyable to even just be in the game.
2. The voice acting is awesome! I don't know if the voice actress is still in contact with you but if so, let her know that she did a fantastic job! It really heightens the game's sense of stakes and makes you feel a more personal connection to your lantern companion (and her reactions felt genuine too---for instance, her reaction to the scene of the corpse boss fight gave me chills, which hasn't happened for me in a flowlab game before).
3. (I think sugarcyube mentioned this on stream) as cool as the massive shotgun is, it would be nice if it was a bit shorter, so that you aren't firing behind enemies that are close to you. Maybe the barrel length was intentional? But then you have enemies like the angel boss that teleports right up next to you (which by the way I think should probably have some kind of telegraphing animation beforehand since it's currently super sudden; the later boss is slightly better in this regard since it has a delay before it reappears). Anyways this wasn't a super big deal, but it was slightly annoying in just a couple of spots (e.g. in a few rooms where you start with enemies really close to you with no space to evade)
Phenomenal work overall, I could probably spend a while just exploring this game (are you planning to add more to the levels after the jam?)