From a tiny balloon-powered boat to a light-following robot, the 18 machines featured in this book cover a wide range of interests and skill levels, and each is designed for action: flying, floating, walking, or talking. Devised by engineers, electricians, and model rocketeers—and explained in step by step instructions—most have elements that you can show off to an admiring audience when they're completed, like a tiny dancing robot, or the hot-air balloon that you can send floating up into an evening sky.