Proportion: building a spiral; using color for legibility
Every object in the drawing has a "group number"; the default is 1. Every group has a color; group 1 defaults to black. Setting the "current" group to something other than one causes new objects to be put into that group. Groups can be set to be drawn in any color.

Still, we are only able to draw points, lines, and circles. The spiral is visible, but we are not yet able to draw it.

Please look at the source code of this page to see these ideas in action.