In this video, artist TM Davy demonstrates how to draw a self-portrait in 11 levels of increasing complexity. As he notes early on, this isn't so much about the mechanics of art as the levels of thinking that go into creating a portrait. Davy defines complexity as "the layers of thinking that help us to build observational truths that are necessary for a picture that somehow feels right".
In his journey towards complexity in portraiture, he starts with the "solar head" (basically a smiley face) and moves to individually identifying features, depicting simple volume & proportion, and the more complex geometry of the human face. From there, observation becomes increasingly important — he uses variations on "looking" or "observing" many times in his explanation — as he covers contours, light & shadow, chiaroscuro, and color.
See also Tony Hawk on the 21 Levels of Complexity of Skateboard Tricks and A Demonstration of 16 Levels of Piano Playing Complexity.