The wireframe stadium at the bottom of page 4 is incorrect.
Created attachment 5176 [details] INFOBROCHURE.pdf
The lines are too fat because the linewidth is set to 0.01 for zero-width lines. We should make this depend on the CTM instead. The disappearing lines disappear because the user space is too tiny, and the comparisons against FLT_EPSILON and flatness (for drawing lines that are dots) fail.