Head over to Target and get the Structural Engineering: Bridges & Skyscrapers for only $29.99! (Reg. $49.99) With this kit of modular building pieces, you can learn the basics of structural engineering by conducting a series of 20 model-building experiments. Each model demonstrates a basic principle of mechanical physics or structural engineering in a hands-on way. Plus, use your Target REDcard to save an additional 5% off and score FREE shipping.