Ages 9 to 12 years. The two dozen contraptions found in this handy resource can move across the land, over the sea, and through the air and can be assembled primarily from low-cost or free recycled materials, batteries, and a single motor. Some of the projects include constructing a hovercraft out of a Styrofoam plate, two corks, and binder clips; building a double-paddle wheeler out of paint stirrers, plastic bottles, and a pair of disposable knives; and turning bamboo skewers, checkers, and a drinking straw into a three-wheeled motorcycle. Each project is clearly explained through materials and tools lists, step-by-step instructions with photographs, and scientific background on the concepts being explored. Budding engineers will get experience working with tools, testing simple circuits, modifying and improving their designs, and building unique contraptions of their own.