Maxis' upcoming SimCity is a decidedly different direction for the franchise, as it requires an always-online connection to play. Every past game, not counting SimCity 2000 Network Edition, has been an offline affair for one player. Each city basically became the same thing no matter what a player intended it to be, and that "lonely experience" is why Maxis has added the always-on requirement.
Creative director Ocean Quigley wants the new SimCity to have a global economy, just like real cities. He explains the shift this way:
If you look back at previous SimCities, they were almost all self-contained. Every city wound up doing pretty much everything. That drove all the cities to a certain level of homogeneity, and all the cities sort of converged onto the same sort of thing over the arc of play. That struck me as being a little sad.
If you look at real cities, they all clearly do distinct things and have identities based around those things. I wanted to let cities differentiate themselves and let them find some way that wouldn't automatically make them converge, and allow them take on unique identities.
Real cities also are not isolated like the ones in past SimCity games. The recent Multi-City Play trailer showed off that aspect, with neighboring cities coming to the aid of one fighting a fire or crime. Cities matter to more than just you, as the entire game world is real instead of fabricated. Quigley likens it to Star Trek's holodeck, where everything that went on had no real impact outside of it.
Players have to unlock a city's higher-level infrastructure by playing for a while. New buildings, work crews, units, and more become available the more you play, and it also makes players think about the path their city takes. It's kind of like an RPG, where you need to experiment in order to see what gets unlocked next. Rather than just spending money to get a new hospital and taking a shortcut, you actually have to sit and play SimCity to get those new buildings.
Maxis has also designed the game to be "modular," with new simulation layers and elements added after the March launch. The PC version comes out first, while the Mac version isn't going to be just a straight port and should take a bit longer.