Two years ago today, a studio called Niantic released a game with a novel proposition: Go outside. Point your smartphone at the real world. Catch some monsters. Within a day, Pokémon Go was at the top of every app store chart. Within 200 days, players had spent a billion dollars on in-game upgrades—the shortest time to reach that milestone by a wide margin. In the summer of 2016, you couldn’t walk two blocks without running into, sometimes literally, a person in hot Pidgey pursuit.