the slopes on the roof pointing away from the light are supposed to be dark, not the ones pointing towards it. they'd actually be lighter than the top plane on the roof.
I get that the lighter part is a plane now, that's kind of what I figured before, but I don't understand the shape of it. it looks like the roof goes (starting in the back, at the bottom)
up a 45 angle slope, flat plane, up a small 90 angle, flat small plane, and then hits the dome. but if you go from the front, you go up a 45 angle slope, and hit the top plane? that doesn't make much sense unless the top plane was pointing towards the front of the building at a downwards angle, having the back end higher. the back would actually be the height of the small 90 angle, and then gradually slope downwards.
maybe this will explain it a bit better.

ugh...took me forever on that roof! it really is confusing!