You were right, I wanted to be relaxed and immersed and this totally fit that vibe. Great example of color/style really resonating with the music.
A few suggestions:
In the first stage where it automatically moves you forward, I kept wanting to push W thinking that made me move forward and also because there was no animation of the seal going up, like the animation where the seal points to the left or right when you press left or right. I think that animation/movement should be the same with the up and down keys on this first stage.
Also in the first stage, I was getting hit by rocks that seemed to not actually touch me. Maybe this has to do with the bounding boxes on the rocks or seal model.
All in all I loved the feeling that I got from this game. Definitely a unique approach to the rewind theme!