Thirty edges, and none of them were ever drawn

What was wrong before this entry: the hero drew an icosahedron by connecting every pair of vertices closer together than a threshold. The threshold was 0.42. The minimum squared distance between any two vertices of that solid is 1.105573. Nothing was ever closer than the threshold, so the edge count was zero, on every frame, on every device, since the day it was written.

It did not look broken. It looked like a deliberate constellation of points, which is why nobody caught it by eye. That is the whole lesson: a defect that produces a plausible picture is invisible to review and invisible to a screenshot.

The cure was to raise the threshold to 1.2 and then to do the thing that should have been done first — execute the constant block on its own and count what came out. Thirty edges, which is exactly how many an icosahedron has.

The rule that came out of it is now standing: a geometric or numeric constant is not verified by reading it, and it is not verified by looking at the output. It is verified by executing the block that consumes it and counting the result. Anything else is a guess with a line number attached.