Apollonian Gasket
Circles packed into every gap between three tangent circles, forever (Descartes' theorem).
Pens
Recursive generations or circle sizes choose the color. Starts with 4 pens and works with anywhere from 1 to 8.
Settings
First circle (× outer), Second circle (× room left), Rotation°, Smallest radius (mm), Outer circle, Style, Fill spacing (mm), Eccentricity, Gap (mm), Pen per.
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.