D Is for Design: The Anatomy of a Down CoatSam Biddle12/17/10 12:00pm2471EditPromoteDismissUndismissHideGo to permalinkIt's light. It's flexible. It withstands frigid temperatures on top of a mountain. And in the entire history of humans staying warm, nobody's been able to beat it. Here's how you build the most powerfully simple jacket in the world.