Very nice work. Excellent atmosphere, felt an uneasy the moment I was dropped into the game. Very nice meeting of the theme.
Nit picks, while the atmosphere did make me scared of cubes, after I defeated the first one and realized they won't fight back it took a lot of the fear away. It was also to dark at various times to the point where I couldn't see where I was going. so a flashlight probably would have been a welcome addition.
A minor addition I would recommend is to look at guiding the player with the environment a bit more carefully, I had no idea where the blocks were, and something to guide me to them would have been welcome.
Otherwise, a very good game. well done.