I didn't really change anything, just liquified it. Just try to imagine looking at a 3D shape from the under side, you will see the bottom part of it. Use contour lines to indicate and suggest the direction a 3D shape is facing. That's basically the concept of the whole thing. I recommend studying some basic perspective concepts and also look up 3 point perspective for figures. If you understand basic perspective, one simplified concept is, anything above the horizontal line, you can see the bottom of a 3D shape, and anything below, you can see the top of a 3D shape.

