Mechanics of Production and Combat are present, but greatly simplified. Exploration and (peaceful) Expansion are NOT present. By the time the player gets here, all the good places to put cities have already been occupied. Research is not an issue, at least in the initial version.
The major focus of the game (both in theme and mechanics) is on Culture (with a sideline in Diplomacy, as that's strongly related). Military conquest is relatively straightforward, assuming greatly superior force. And the player will start the game with sufficient military force to easily conquer some of his immediate neighbors right away. The really interesting part is not the war itself, but the decisions that build to the war, and those in its immediate aftermath.
After you conquer an enemy city, you are given three choices: Genocide, Enslave, or Assimilate. Genocide is the simple way to take all their territory and physical infrastructure, but has the critical failing that you lose the potential population growth. Given the timescale of this game, population growth through breeding is a minimal factor at best; you really want to get conquered people working for you. The simple way to do THAT, is to Enslave. Slave workers, however, are not very efficient, and you also need to allocate a significant amount of your military to police functions, to keep the slaves in line. To get the FULL benefit of your increased population, you need to Assimilate them as citizens. This has its own difficulties, of course.
Most of the player’s actions outside of conquest consist of shaping the Culture of your civilization. Your Culture will have opinions, possibly strong ones, about Genocide versus Slavery versus Assimilation. They will have all sorts of other opinions as well, which may initially seem largely pointless, but which help define your cultural identity.
In the build up to a Conquest, one of the most crucial points is how your cultural identity compares with that of the target city. If you move your own Culture away from theirs, and paint them as completely barbaric, that gives your own soldiers bonus strength in combat, but makes it almost impossible to Assimilate the target afterwards. Conversely, if you try to make your culture similar to the target’s, your soldiers will be less enthusiastic about fighting, but Assimilation is far more possible, and will go more smoothly, afterwards.
Ultimately, the winning player is likely to be the one who has the largest definition of “us”, the most all-encompassing cultural identity. Though their soldiers are actually the least efficient, this is more than compensated for by the number and productivity of their workers.
My design goal is to demonstrate interactively both how demonizing the Other is an attractive short-term political strategy, and how EMBRACING the Other outperforms it in the long term.