Cool idea! It took me a bit to figure out what I had to do with the boss, but that was a nice "aha" moment. However, the movement bug made a lot of the rest of the game frustrating, and it made getting past the second guard beyond the door impossible to hit without dying.
Another thing worth mentioning is that the text in the top right, as well as the sun behind the wall, jitters whenever the camera moves. I'm not sure if this was intentional, but if so it's a neat effect.
Finally, and most importantly, I think the Wilhelm scream fit perfectly for character deaths.