WARNING: SPOILERS AHEAD
Figured out the Gloop thing, it was just a skill issue after all haha. Spikes doing 4 damage sure is brutal o.o I was able to get the Voltanium Shard but I couldn't get out :B My first Metroidvania was Metroid Fusion so I'm probably just too used to all the quality of life stuff in modern games.
I'm sad the demo is over, but I'm excited to see what comes next.
That being said, I have one more suggestion:
• Perhaps the bestiary could have the sprite of the enemy on the menu, otherwise just choosing from numbers is very ??? Some enemies are larger though which might make it more complicated, there would need to be less entries on each page.
I also did find (possibly) 2 more glitches:
• I've noticed that killing a Karkanon while it still has a shot on screen causes the shot to stay still and linger.
• I'm not sure what caused it but I noticed that there was 2 occasions where I had 4 out of 5 health and picking up another health caused me to drop to only 1. I've not had it happen any more times though, I dunno if I didn't notice getting damaged since I was playing it while tired.