I've reached the end, and here are my thoughts:
I like that you can use your healing nodes to also create a special attack, and that healing is readily available as long as you can find an enemy to hit. However, I do think it is also a little hard to realize that you have healing available as an option, because while it is listed in the bottom left, it only appears if you have 3 nodes, and there is no tell that you've built up enough to heal. Maybe a slight glow or change in color on the character would help players immediately tell.
Enemies might be a bit bulky for now. I get that may be to allow you to build up healing, but it does mean some 'backtracking' takes a while unless you choose to just jump past the enemies.
The eye watching you from the back looks very cool, and did give some presence, although I'm a little disappointed we don't get to fight them.
I understand the theme was minimalism, and there were some places where it was clear when the rooms changed, but a lack of landmarks sort of made it hard to traverse sometimes, especially since the gimmick of the game is that doors do NOT lead back to the same room you entered from. I do think the gimmick is cool, it is just that I accidentally cycled past the first boss several times, because everything shares a similar palette (for understandable reasons).
Overall, I like it. Good job.