This is really great! I love so many aspects of this game, definitely underrated. The grapple is fun to use, all the weapons are satisfying and unique, there's a good variety of enemy types, and there's just so much content! I wasn't really sure what my goal was, but I got to 56% completion and had to pause. If I could give some feedback and things I noticed:
There was one enemy I killed (XP dropped) but didn't disappear, I think it was pretty early in my playthrough in Shallow.
I feel the speed of the player could be slightly faster at the start. While the movement speed upgrade was great, I think base speed could be a little faster just so that it's not too tedious and slow.
I'm not too sure I agree with losing XP on hit. I would say it's a little more annoying than fun as it's quite punishing, especially if you're weapon is at max level--just one hit and then it's downgraded to lvl 3 which doesn't feel good. Maybe only lose XP on death? Or ensure once a weapon reaches a certain level, it can't be downgraded?
Moving around in Shallows was quite difficult, especially when there's nothing but ceiling to grapple onto. That one long room with spikes on the floor could probably benefit from some platforms in the middle? Just to make maneuvering more fun while still maintaining that challenge you likely intended for. Maybe there's an upgrade later that I missed or haven't gotten that helps? Not sure.
Overall, I really love this game! The metroidvania aspects are done really well, the combat feels rewarding, and the graphics and audio just added to the experience. Really well done, and congrats! I will definitely come back to continue where I left off.