First off, I want to say that I am a pretty big fan of the game you develped so far. The idea of a God being stuck in one's own mind is certainly a unique and interesting idea, and out of all the games, I personally think this game does a really good job of interweaving the narrative into the gameplay and drive the player to collect the fragments. It would be nice to see what kind of "memories" will be shown to be player and as for now, it seems to just be an objective to gate progress. This actually reminds me of more action-based RPGs -- Kingdom Hearts comes to mind with exploring "dream" worlds, especially with the fragments and the area after the tutorial.
It would be great to see how the hub idea gets expanded. A list of the various location, maybe fast travel to areas already visited, and an indicator of how many fragments were collected at each area (assuming you don't have to collect all of them to move on) would be a nice way for the player to keep track of what they found so far. Also, since you guys already have some sort of inventory system, it might not be that hard to extend it to other collectables (maybe with powerups or temporary buffs/boosts when the combat system gets fully implemented). They could also help with the "memories" aspect as certain items can unlock a certain memory or act as keys to unlock hidden areas or even one big (final) area when multiple items are collected from various levels.
However, there are certainly some slight annoyances when it comes to implementation. As someone mentioned, the terrain collisions with the player can range from a pain to get unstuck to completely interrupting the experience (especially in the after-tutorial area) since the main character would not be able to free themselves (jump does not work and visually, it doesn't even look like they are stuck in anything since there was just open space). Though, I did not encounter jittery camera issues and the camera control was fine for the most part (the close zoom-ups sometimes do feel odd).
The barrel puzzle...was quite a hassle. There was a tin bottle and a barrel, and only the barrel seemed to matter. There were times when the barrel would roll down the slope, and it was weird to roll the barrel back up. First, the player had too little mass (or everything had too much) so rolling would actually cause the player to roll up the barrel sometimes. Second, the collision wall to prevent progression got in the way of getting the player on the other side of the barrel to push it up the slope since the barrel would be against the collision wall. This was another confusing part of the tutorial since I initially did not know why the collision wall was there in the first place. The tutorial prompts were nice and helped to hint on what we needed to do to proceed, but being limited to just small squares on the ground as triggers could have been frustrating if I didn't notice it early on.
Overall, I think there's a lot of potential and building up the idea of collecting fragments and doing something with them (like unlock memories, perhaps as journal entries or something) instead of just an objective would certainly convey the story a bit better. The controls are certainly wonky at times, but I do believe this game can turn into something truly great -- just continue what you have currently, and it should work out in the end. The textures and environment (at least with the cave and lighting) look awesome and the playable character has a cool design with the side blades (why punch when you can just slash stuff with them), but jokes aside, it would be nice to see if the enemies have a similar design with accented colors that almost glow, contrasted with the darker tones that gives an almost deep underwater feel. Oh, and maybe extend the punch animation length (and apply it to a greater effect area) and add some animation to the jump.