Ingress

Ingress is an augmented reality massively multiplayer online role playing GPS-dependent game created by Niantic Labs, a startup within Google, originally for Android devices, and since July 14, 2014 for Apple's iOS. The game has a complex science fiction back story with a continuous open narrative. The gameplay consists of establishing "portals" at places of public art, landmarks, monuments, etc., and linking them to create virtual triangular fields over geographic areas. Progress in the game is measured by the number of "mind units" (MUs), i.e. people nominally controlled by each faction (as illustrated on the Intel Map). The necessary links between portals may range from feet/meters to miles/kilometers or hundreds of miles/kilometers in operations of considerable logistical complexity. International links and fields are not uncommon, as Ingress has attracted an enthusiastic following in cities worldwide amongst both young and old, to the extent that the gameplay is itself a lifestyle for some, including tattoos.

Ingress is estimated to have 34 – 16k players a day. Around 20k – 2m accounts have played it in total. No Steam data is published for this game, so the range is modelled from the size of its Discord, Reddit, Twitch, YouTube and app-store communities. It is a rough band rather than a measurement.