Just finished getting through this, was pretty good. I made a sample map from the main corridor and tried to figure out what the rooms were. After getting similar areas done, ran into some that didn't work in that method and elimination for others. Thought two areas were an area, wasted the key, obviously knew after being in it.
The concept is pretty cool, can cause you to panic if you go in unprepared, trying to remember which next key is the one you actually need. After doing the map thing, just prepped in advance, key is 5 down? Enter room, press down to get it quickly, run past.
Went in again without losing any keys, though don't know if that does anything, got two different endings. Would continue playing if there is more, but hard to tell without just running around with no idea. Was fun.