Three panels of identical greys that refuse to look identical: the classic surround, White's illusion — which lateral inhibition cannot explain — and Adelson's checker shadow. The test value is a constant the music never touches, so every apparent change is manufactured by the viewer.
Drawn with: a WebGL2 shader.
Reacts to and looks like: gpu, webgl2 and audio-reactive.
Family: Visualiser.
Runs in your browser. The preview above is the same program the renderer uses.