Start your engines! It"s easy to snap together these two air-propelled racecars that really soar over ramps and ridges. What makes an air-racer go? Explore the science behind electricity, electromagnets, and propellers while building two fun racecars! Race yourself or your friend on the gravity-defying racetracks, tunnels, and homemade roller-coaster ramps described in the book. Or make an amazing air-racer course of your own!