Moiré
Overlaid circles, gratings, spirals or rays whose interference draws giant fringes.
Pens
Each line family gets a palette, split into broad bands as more pens are added. Starts with 3 pens and works with anywhere from 1 to 8.
Settings
Pattern, Spacing (mm), Sets, Offset (mm), Offset direction°, Rotation between sets°, Spacing change (%), Alternate handedness, Wobble (mm), Wobble size (mm).
The preview uses the default settings on A4. Press R in the app for random variations. The SVG export is in millimetres with one Inkscape layer per pen, so it works with the AxiDraw extension, vpype and saxi.