The no. of teeth in the ring and wheel are controlled using the sliders (top right) click USE to apply changes. Click on a colour for drawing and on the hole in the wheel to be used. The knob control can be used to align a peak to an existing drawing.
When ready click on the START button. A progress bar will appear showing how much has been drawn. While drawing only the HIDE COGS and speed control slider are active.
Each drawing overlays previous drawings until you click ERASE GRAPH.
The GUI controls are created using the G4P library see http://www.lagers.org.uk/g4p/index.html
To tweak this sketch, first download it.
Make your updates, then upload your tweak!