This document discusses using game design principles in products and public campaigns. It provides examples of a toilet game to reduce spillage, a basketball trash can for fun trash disposal, a bottle bank arcade that collected much more bottles than a regular bank, and soap with toys inside that reduced illness in children by encouraging more frequent hand washing. The document also discusses nudging people to voluntarily do things for a purpose without directly telling them, and proposes a subway door game to discourage people from trying to enter at closing time through a visual danger effect, though that may backfire by thrilling some people.