On July 19, a dozen teams gathered in hackerspaces around the country to await the rules of a 72-hour build competition. Red Bull, the energy drink brand and sponsor, announced the challenge at shortly after 6 p.m. Pacific time: Construct a game of games. It must be physical, not virtual; weigh less than 2,000 pounds; and have a clear winner. Inside the Mill, an industrial-arts shop in Minneapolis, Nathan Knutson, leader of the 1.21 Jigawatts team, and the rest of his 23-member squad began whiteboarding ideas. It had been a blazing hot summer, and by 2:30 a.m. all they'd settled on was making something with water.