two rectangles crossed out and embellished by an X
Communicative Choreography -- More than Rectangles
The Hypertext turns 50
More History
Paris
Rectangles, Circles and Tangents --
Apollonius, Archimedes, Voronoi, Kuratowski and the gang
Circles, Tangents, Lines, Intersections, Polygons, Segments and Glyphs --
open source software
Afterthoughts:  
Specs: (exclusionsshapes),  
Examples:  finding polygons, bloat-wrapping, pages and glyphs