That sounds very interesting, I remember such course when you had to do quick sketch and given such short time so that people do not concentrate so long on the fine details but see the object as a whole and pay attention to distinct features. That is a lot of fun, Like how you made David, immediately recognizable pose, like the sitting person, really nicely done legs, the laying person, the feet done so well. Feet and hands are two difficult anatomically parts of human body. Nice exercise :)