I like how simple yet effective it is. It really feels physicambianceally uncomfortable, it's cold, in a way claustrophobic and immersive. I think the diminishing light and ambiance contribute to this the most.
To me, the biggest flaw was how confusing and difficult it was. Like if there were at least some sort of signs or rememberable elements to the level, it would help tie in players' progress to something they remember and thus making it a little less frustrating. But then from the ideological perspective, it does its job of making the player feel uncomfortable and wanting to find comfort really well.
Amazing entry!