That was an experience, for sure.
Controls were a bit challenging: With the mouse visible, when I got to the edge of my window I couldn't turn anymore. So I had to right-click at the edge of the screen to re-acquire my cursor, then move it to the centre, then continue turning.
Other than that, there's a lot to like.
At first, I just saw a white screen with no indication that my controls were working, so I assumed FPS and marched forward. I started to question my sanity when I wasn't sure if I was walking toward something real or imaginary (Is that an in-game object or a bit of dirt on my monitor?). Eventually I got into the game-proper and enjoyed the experience.