William Gurstelle is the author of Adventures from the Technology Underground, Backyard Ballistics, Building Bots, and The Art of the Catapult. The number of hours he’s spent crafting fighting robots and catapults instead of working at, say, his normal job (as an engineer) is, in Bill’s own words “scary to contemplate, but it serves a purpose.” When not building devices that make stuff go whoosh, boom, and splat, Bill is a contributing editor at Make magazine and writes frequently for Wired, The Rake, and several other national magazines. He lives in Minneapolis.