To get some a game-breaking issue out of the way upfront: I managed to get myself stuck and unable to move a few times, somehow. I wish I had repro steps to help you figure it out, but it happened once right after the first text box (I hit some buttons during it, maybe that did it?), and once at the third checkpoint.
Once I actually got going, without running into those issues though, I really dug the game. It looks amazing, and controls nicely. The interplay of trying to make the area safe enough that the possession wouldn't kill you and trying to progress made for a good amount of tension. I got big Celeste energy from the game as well, which I loved.
As a small polish note, I had some trouble navigating the initial menu, where the mouse and wasd didn't work to navigate, enter selected, and only space seemed to close them. I also had a little trouble distinguishing between the background and the foreground at times. Most noticeably, when I got to the third checkpoint, I thought the support beam in front of it was a gate I'd have to unlock some how (the lever super close by may have primed me).