Quadrilateral Spiral
Inspired by the beautiful spiral of kites in @tilman's Geometry Daily #449 http://geometrydaily.tumblr.com/post/51559173812/449-archimedes-turbine-a-new-minimal-geometric
In this sketch you can have any type of quadrilateral ABCD. With the tool, click 4 points, and the tool will construct a new, similar quadrilateral on the edge between the 3rd and 4th points. Then you can use GeoGebra graphics controls to color and decorate.
What can you make?