Experience the forces of gravity, magnetism and kinetic energy through play with the Ravensburger GraviTrax Starter Set, an interactive marble track system that provides endless opportunities for your kid to learn and experiment through hands-on building. The GraviTrax Starter Set provides nine models to build and 24 tasks to tackle, all with varying levels of difficulty—or your creative kid can freestyle their own marble runway. (Storage-wise, you might want to transfer pieces into resealable bags as the original packaging doesn’t keep everything contained, but the box is sturdy and storable whether in the closet or under the bed.) A four-piece mat is the foundation for durable track pieces that stacked easily, making it an activity kids can do solo. Although some pieces in shades of white can be hard to differentiate based on the construction booklet, a little trial and error will encourage problem solving to get those marbles rolling again.