In regards to the heuristic, it is something you'll get more comfortable in judging with experience - but in general, focusing on what it means to be simple versus complex may help. A line that maintains a single trajectory - like a simple arc, unchanging throughout its length - is inherently simpler than a line that follows a trajectory, then suddenly incorporates a little cut into its path, and then resumes the same trajectory.

You can also refer to the concepts from the Principles of Markmaking - the third for example addresses the matter of zigzagging quite specifically.

As to what you said about using the previous phase of construction as a "guide" - what we're doing here is fundamentally the opposite. Every step involves establishing a solid structure in 3D space - something we actively treat as though it exists physically. So for example, the by the second step of the leaf construction exercise (as outlined here), we have a structure that is akin to having a leaf shape cut out of a piece of paper. In the next step, we add edge detail to it in a variety of ways, all of which occur in 3D space:

• We can lift or droop sections of the edges to create a wavy edge.

• We can add protrusions - yet more pieces of paper stuck on - to have little spikes come off the edge.

• We can physically cut with scissors into the shape, where the lines we're drawing denote the path the scissors would follow.

This is core to the course as a whole - we are not sketching loosely, nor drawing. We are building in 3D space, and the visualization of what we build is what ends up on the page.