If you look closely, that is some seriously messy, down-n-dirty, rough sketching. Not everyone can design (and there are a million other things I can't do, that other folks kick butt at), but, anybody can sketch like that.
My first 3 sketches were in black and all laid over each other. A bit
cornfusing.
When that happens, I overlay again but go to different Flair pen colors to help distinguish between layers.
Once I got my second upper floor revision sketch worked up, all I saw was purty colors...!