A drawing is evolved through the growing, dividing and joining of shapes.
Ripple grows a drawing by adding layers of outlines that hug the existing shapes.
Petal grows a drawing by adding simple U-shape or tear-drop-shaped outlines. Each petal is formed with a single line. Petal can add a sense of dynamic and movement.
Wrap grows a drawing by adding non-hugging outlines around existing shapes.
Ribbon thickens line segments.
A hole divides a shape into part rock (solid area) and part paper (see thru area).
Skeleton divides the space inside an existing shape by adding scaffolding lines or segmentation lines. Scaffolding lines are like internal skeleton. They can look like the bone structure of a person, or the vein structure of a leaf. Segementation lines are like external skeleton, such as the shell of a bug.
Connector are simple line segments that connect disjoint shapes to form a unified one. A ripple or a wrap can perform the same function by drawing an outline around multiple existing shapes. Connector does the same by adding line segments in between shapes.