Popmilo the idea is left part much more darker. Here, for example, you have left in luminance4 and right with luminance12.
And more, if the roof has a darker/pale colour like here the lilac together with one or two scanlines between floor same luminances but other colour you get a perspective of the building one side|corner|other side.
Of course this isn't really corners as it's all at the same scanline(s) and not isometric 2,5d but it can fool our vision.
Perhaps it's just me seeing this but you can abstract from what you already know and like me when I first run this and I was not expecting.
Do not know, what you try to tell us. If you think about two surfaces, one brighter than other, the obvious is that we see it as two surfaces at different angle to the light source. The effect used all the time in games. Here is simpler one. There are some FX effects in demos showing hanging "rope" which rotates ad jumps like rubber rope. Those are the same IMO like you talk about.
Well, I also don't know what is special in that picture you've sent. The use of darker colours to make an impression of "false 3D" is really quite common in games. Take one element of my graphics from Ridiculous Reality as an example (in attachment) - the right side surface of the hanging block is made using very simple rule - every pixel is one tone darker than a corresponding pixel from the front surface.
