Chromaroma uses an existing infrastructure—London’s transportation systems—as a platform for a real-time game. Commuters sign up to play using their Oyster cards, a form of electronic ticketing used in Greater London, and then are grouped into one of four teams, where they rack up points with each journey and strategically complete specific tasks and missions. Some missions rely on an evolving story line (such as a diamond heist or a ghost hunt), and others have players altering their daily routines (getting off a stop earlier or going all the way to the end of the line) in order to gain a new perspective on the city. The players’ physical movements are recorded by their Oyster cards and can be charted on three-dimensional interactive maps and published on Twitter or Facebook, making everyday journeys into social experiences. Chromaroma thus injects the often mundane process of commuting with a sense of playfulness, encouraging people to explore the city and ally themselves with strangers. Since it does not rely on smartphone technology, the game is accessible to anyone with an Oyster card; the design company Mudlark hopes eventually to expand Chromaroma to other cities around the world.