To encourage people to take the staircase instead of the escalator, Volkswagen converted a set of steps at the Odenplan subway station in Stockholm into working piano keys. The effort is just one stunt in DDB Stockholm's Rolighetsteorin.se or "Theory of Fun" campaign, which showcases efforts to get people to change by simply making things more fun.

DDB Stockholm CD Andreas Dahlqvist discusses the "Theory of Fun" effort further here.