We all know them from our childhood days - those brightly coloured plastic spirals that would slink from one step to the next after being pushed over the edge of a flight of stairs. From today's perspective, it might be baffling how such a simple toy could so fascinating. Truth be told, we cannot exactly pinpoint why the Rainbow Spring fills us with joy and happiness. Maybe because it transports us back in time - or maybe because as nerds we can use it to demonstrate physical principles like kinetic energy, momentum or inertia ;).