Take the Rube Goldberg challenge! Toppling dominoes, rolling marbles, racing balloon cars, springing catapults, and whizzing zip-lines are all elements used to build Rube Goldberg machines in Crazy Contraptions: Build Machines that Swoop, Spin, Stack, and Swivel with Hands-On Engineering Activities . Middle schoolers love the wacky machines designed by Goldberg, which were based on complicated chain reactions used to accomplish very simple, sometimes ridiculous, tasks. Young engineers are invited to invent, design, create, and play as they make their own Rube Goldberg machines using the engineering design process and lots of imagination!