With over one hundred pieces and nine potential construction plans (plus whatever little engineers dream up on their own), the GraviTrax marble run set provides endless building, reconfiguring, and racing good times. It draws on STEM skills by giving kids hands-on experience with concepts like gravity, magnetism, and kinetics, and there’s some creative thinking needed, too—not that they’ll notice that. Kid builders will be too busy experimenting with height and trajectory and perfecting their twisting and turning race course. Expansion sets let a race track reach a grander scale, and accessories like a trampoline and cannon amplify the fun.