Most people haven't yet heard of Ingress , an augmented reality game currently being beta-tested by Google . But think of it as a digital version of capture-the-flag, in which players from a blue team and a green team use their mobile phones as they move around the real world, trying to find and claim ownership of "portals" to another dimension.

Not surprisingly, a lot of squabbling over portals happens around Cambridge, and on the MIT campus.

Over the past few days, in the wake of Friday's shooting of MIT campus police officer Sean Collier, Ingress players made two decisions. They called a temporary ceasefire on the MIT campus, turning it into a neutral zone. And they created a memorial to Collier near where he was killed at the Stata Center.

Last Saturday, Christopher Davis, an Ingress player and Google employee, posted a message suggesting that two portals be placed side by side, one from each faction, near the Stata Center on Vassar Street, and also at Copley Square. "Nothing could be a stronger statement that 'We are Boston. We are united,'" Davis wrote in a posting to the local Ingress forum. The two teams worked in partnership to set up the memorial; it was completed around midnight last night.

The Copley Square memorial hasn't yet appeared. "There hasn't explicitly been anything set up in the game around Copley or Boylston Street," explains Ingress player Stephen Lewin-Berlin, a managing director at Quanta Research in Cambridge. "You have to be within 40 meters of a location to do anything, and all that area has been a crime scene." Until the past day or two, at least...

Lewin-Berlin tells me that the idea of making the MIT campus a neutral zone, and setting up the memorials, wasn't exactly uncontroversial within the Ingress community. "For some people, this is an important symbol," he says. "But for others, Ingress is a way to play and get away from real life. There were some interesting dynamics in the discussion group and the in-game chats." Lewis-Berlin says he hopes the ceasefire and memorial will endure for a week.

The screen-capture above is from the Ingress Boston community on Google+, which has 196 members. A memorial service for Collier is scheduled to take place today at noon on the MIT campus; Vice President Joe Biden will be among the speakers.

