I needed this. I don't really like the patronizing from the beginning but it does good in showing the flaws one makes often and more importantly guide us in the way to correct them. Observe and practice. Nsio explains: Foreshortening by Nsio
An sculptural interpretation of the planar head affected by various directions of light. Note how the light effect directly correlate with the planes of the sculpture. Drawing a cube is like drawing a head.