Twelve mechanisms on one drafting sheet, all turned by the same crank at 20 RPM: slider-crank, Scotch yoke, Geneva drive, quick-return, cam, escapement, and the Jansen and Klann linkages that walk. Four seconds in they all stop on the same crank angle, the sheet is wiped, and the film rebuilds each one part by part — crank, then rod, then piston, then bore — letting the drawing prove a fact about the machine before it is allowed to move. Nothing inked is ever un-inked, so the last shot is the only moment with all twelve running at once.