He’s standing behind a four-foot-high steel trebuchet (a relative of the catapult). “Fire!” he cries and sets the balloon hurtling across the open workspace. Some 25 feet away, a colleague holds an iPad like a shield and deftly intercepts the flying balloon head-on. Happily, the balloon bounces off without rupturing. The tablet emits a recorded sound of shattering glass; a broken-window image fills the screen. “Fantastic!” Winter shouts with unrestrained glee.