Short and simple.
I liked the use of darkness.
But in my stubbornness, I just kept going into the dark area from the start, until I gave up and checked the left area. Maybe put some indicator that there is something on the left, or position the elevator so you can see it from the start. Alternatively, concentrate tutorial messages at the starting area. Right now, their positioning gives the impression that you should go through the dark area from the very beginning.
Aside from that, it was relatively smooth sailing.