Well, mods have enabled walkable cities for some years, but it didn't work well. Recently, the modders of SimCity 4 invented a new way of building walkable cities. And I have to say, it's pretty fun.

SimCity 4 is a game that has well-internalized the automobile-centered urbanism of the United States. But despite these faults, community interventions through game modification can allow players to design entirely new urbanisms in the game that breaks with car-centrism.