The game asks players to choose between the Resistance and the Enlightened, two global teams battling to control the flow of a mysterious energy that has begun to propagate throughout the world. Players are tasked with hacking and capturing portals, sources of the mysterious energy that are often located near public buildings or landmarks.
Ingress is intriguing primarily because of its unique gameplay, which requires players to actually explore the world. To capture a portal at the Statue of Liberty, for instance, a player must physically go there with their device -- it cannot be done from a couch or easy chair.
Groups of players can also band together to increase their power, capturing portals over a wide area. Some Ingress players have been known to organize outings that resulted in the capture of an area spanning multiple countries and hundreds of thousands of square miles.
Initially release for Android in 2012, a number of unofficial Ingress ports have been available for iOS from the beginning, though many required players to jailbreak their iPhone or iPad. In either case, using the unofficial apps often resulted in a ban, limiting their appeal.
Ingress version 1.53.0 is available now as a free, 43.7-megabyte download from the App Store.