Gust Flag

a flag toggle. press it and the flag runs up the pole, a gust rolls along the cloth with a halftone fill riding behind it, and the tails throw three splashes.

key insight: the cloth is described once in its own coordinates, along it from the pole and across it from the top edge, and every point drawn goes through one warp. so the outline, the solid fill, the halftone dots and the spots the splashes leave from all bend by the same rule and cannot disagree.

a raised flag never stops fluttering, and the halftone stays after the fill as the light on the folds: where the wave tilts the cloth away, the screen punches through. move the pointer past it and the pointer is wind.