Over the course of three months, a "MegaBot" took shape at the Boston makerspace Artisan's Asylum. Stroup was the primary builder, Cavalcanti acted as designer, and Matt Oehrlein, an electrical engineer, handled the electronics and code. The first prototype, made of welded steel covered in sculpted foam, was just a torso on a trailer. An updated model stands 15 feet tall and can roll forward on treads at a lumbering 3 mph. This second prototype holds two humans: A pilot controls directional movement, and a gunner rotates the robot's torso to aim and fire the swappable, arm-mounted weapons. These include a pneumatic cannon that fires 3-pound paintballs and a launcher that can shoot 20 smaller paintballs in a row. If one arm falls off, the other can keep fighting.