That same night, a rooftop full of friends convinced me to download "Pokémon Go." At first, I didn't have much interest in the actual game (I'll admit, that's changed), but I'm fascinated by the way people negotiate the built environment. And as inane as "Pokémon Go" might seem, its effect on the way people use, share, and discuss public space has been profound. It's also wildly addicting, largely because so many people are playing (the game surpassed Twitter's daily active users less than a week after its launch). Even if you don't really care about catching a Pikachu, it's hard to resist joining in the fun of a collective obsession. I imagine this is why agnostics default to whatever religion they happen to be surrounded by, or why half the city pretends to care about the outcome of sporting matches that don't actually affect anyone's lives.