The new SimCity, due for 2013 on PC and Mac, is powered by a new proprietary engine called GlassBox. It is described as "a new data-driven simulation engine" that is Maxis' "bet for the future." At a panel during Game Developers Conference, the studio detailed how GlassBox will power the upcoming SimCity "reboot" and promised that the modding community will be able to get their hands on their powerful new tools.

"We're huge fans of our modding community," creative director Ocean Quigley told the audience. "We've designed all this stuff to be moddable."

"We know modding is hugely important to our community," Quigley noted. "We know the reason why people are still playing SimCity 4 ten years later is because the modding community has kept it alive. GlassBox is built to be moddable, but beyond that we haven't announced anything"

While coming short of announcing full mod support for SimCity, Maxis did add that "we're using the same package format The Sims and SimCity 4 used," showing Maxis' desire to make it easy for Sim fans to transition to GlassBox tools.