A hand-painted wooden contraption where marbles loop endlessly through ramps, a paddle wheel, a funnel, a see-saw and a spiral drop. The path is a single parametric polyline sampled by arc-length so any marble's position/direction can be looked up as t in [0,1); gravity is faked by boosting speed on segments whose direction vector points downward (steep descents = faster rolling), and rolling spin is derived from travel distance divided by marble radius.