This is a really neat little game! I like that there was a focus on the atmosphere here - not necessarily trying to make it scary or anything, but subtly unsettling. Unnerving, but still calm. Gave a unique feeling that I enjoyed a lot. The music helped with that a lot - it was perfect for the game. Chilled out, not desperate or energetic, but it still had momentum. Great job with that!
I also thought the gameplay was interesting! Simple and straightforward, but there's nothing wrong with that whatsoever. It did a great job of not introducing too many different things, keeping the core gameplay as the focus. I like that it made you think and be patient without being too challenging. Super simple concept that was very well done here! And the detail that the shadow is far more sensitive to light than the body is to dark was interesting too, I liked that.
Couple of things to note, however. To start with, (and this is almost certainly because I use an ultrawide monitor) the little blurbs (I think they were blurbs, I don't know) that would show up on the bottom of the screen sometimes were completely cut off for me. I could only see the top of the box, and not really a whole lot else. I don't know if they were telling me controls, or story, or what. Like I mentioned, it's likely because I'm using an ultrawide monitor, it's caused problems for a number of other games as well.
I don't really have anything else critical to say. Overall, I really liked this game a lot, excellent job!