Being able to tilt more than 90 degrees would descrease the player's sense of orinetation.
It looks like you add the door models in a room not when opening a door, but when you enter it only. that looks weird. Or are they lit weirdly?

Sometimes looking at a door not ahead, but to one side, lets you move straight from the door you're in to the door you're looking at, sometimes the camera will move to the middle of the room first. I didn't get that O.o

Other than that, cool, quick controls, nice Sound effects work as well, and I like the cubes.