The only diffraction grating in the catalogue, and the reason it is a building rather than a panel. A grating splits light by wavelength across the angle you view it from, so what it returns depends entirely on where a surface points — and one flat panel points one way and shows one colour. A pleated facade points a hundred ways at once, so the whole spectrum is on the building at the same moment, a band to each flute, and the bands travel around it as you move. The film is embossed with parallel grooves, and the fan opens across them.