3-in-1 engineering kit: Assemble three cool robots, wind them up, and watch them go--no batteries required! The models are powered by a mainspring, the main device found in old-fashioned clocks. Models include a race car that drives up to 60 feet, a robot that walks up to 20 inches, and a countdown timer that counts down up to 6 minutes. Learn about potential and kinetic energy and how gears and springs function in different mechanical devices. Includes a 64-page, full-color manual with clear language, simple step-by-step illustrated instructions, and scientific explanations.