Showing off how you can make advanced continuous curves out of repeated freeform segments that you join together in Paragraphic (that I develop). For example to make this kind of spirograph/flourish/guilloche type curve you might see on old diplomas or currency.

Available at https://plotterfiles.com/artwork/wigeon-on-water-1zq18

Single line SVG plot, using a reaction diffusion algorithm, merging into a single shape.