to be sure we haven't missed any possibilities,here's another way

We know the control panel has to be as high up as possible,so let's make our way down the pyramid.The fifth highest floor doesn't work either.We can figure that out by drawing it,but to be sure we haven't missed any possibilities,here's another way.Every door corresponds to a line in our graph that makes two rooms into neighbors.So in the end, there have to be an even number of neighbors no matter how many connections we make.