The city as a giant playground? I think that’s more than just a fantasy in times of alternative reality games and the street running movement. This morning I was introduced to a less live threatening and perhaps nicer approach to urban fun I by a charming philosophy professor on the subway. He is part of a movement called invisible playground. They are designing urban games especially for Berlin. You want to play? Then you should check out the 100grad festival at Hau this weekend. You can read more on when and where the games start here. A nice video of one of their games after the jump.