Great controls, great concept, great graphics, great audio, and great overall feel. I had an amazing experience playing this game.
I wish you guys can make many more games as good as this.
*Some spoilers*
After the first checkpoint, where you first get to the big "open" chamber, I died so many times. There I understood that this game was about patience and controlled risk taking: sometimes you have to jump and take it.
The monster inspired a lot of terror, way before seeing it in action.