The gravity defying Fridge Rover will move over any magnetic surface. All you have to do is wind it up and watch it go. Inside the Rover's clockwork mechanism is a coiled spring that winds more tightly as you turn the handle; this stores energy in the spring (potential energy). When you let go, the spring uncoils, releasing the energy again and making the wheels turn (kinetic energy). The wheels grip the surface because the magnet pulls the Fridge Rover firmly against the fridge. A magnet and wind-up vehicle in one gadget, this toy ensures that your refrigerator door stays interesting! Great as stocking stuffer or party favor, the Fridge Rover is a great gift for young and old minds alike.