I've started thinking about culture - the kinds of norms and judgments and responses that a society builds. To a large extent, the culture of a society dictates a lot more or the society's behavior and growth patterns than the technological or economic state of the society. Of course, the culture is strongly influenced by technology and economy...
I was thinking about whether you could use this in a game. Instead of building your game around technological research and building new buildings and shooting at people, could you replace those systems with one where you define and alter the culture of your people? Could you make a game where the people act largely autonomously, but guided by the culture you have crafted? Furthermore, as the situation changes... would you buckle under the pressure of the culture you initially created, as you struggle to make it suitable for the new situation?
Let's say that the game is sort of a fantastical game - not a fantasy game in that there are orcs and dragons and things, but more of a dreamlike game. You create a little village full of, I dunno, elves or something. And then you guide their culture so that their growth and interactions with other tribes goes vaguely well.
I think a big part of the game would have to be in factionalizing. That is, breaking the population down into subsets.
You can make a cultural rule "do not kill", but that's a pretty strong restriction and, in most cases, you'll probably eventually want to kill some people - invaders, bandits, sheep, whatever. So the answer is to create a subset of people who are allowed to kill, and then control the culture such that the murderous subset only comes into play in specific situations, and maybe even include some "clean up" rules to prevent weakening of the overall "do not kill" norm. IE, "police can kill" with an event trigger of "if a police officer kills someone, they are no longer a police officer", which would relegate them to the general population and prevent the police subgroup from developing serial murdering as a common trait.
By creating a lot of different groups and gating which groups can funnel into which groups at what times, you can create a societal "machine" with rules that automatically regulate its behavior. The machine reacts to pressures both internal and external and the society flows along the path that carves. Of course, this machine is not made of unbending metal - particular groups will gain or lose traits, corruption, and/or authority as the machine moves along. Understanding how this tarnish builds up will allow you to build a society which lasts longer.
Because, inevitably, the society will fall apart. The core rules you build cannot be simply peeled away - it takes a huge amount of effort to change a rule, once made. All you can do is add more rules. Patches. Eventually, the society will not be capable of reacting to the stresses it was originally created to react to.
Of course, the fun lies in the route between here and there. Not only is there a lot of choice as to what sort of society you want to set up, the stresses are going to be radically different depending on the environment you live in, the number and aggressiveness of your neighbors, and so on. If you want to set up a tiny hippie community on a tropical beach that never grows one iota, there's no judgment from the game that says its a bad idea. A small, unchanging community might be a good idea, actually, because it'll have fewer internal stresses. Of course, small communities tend to get ripped apart by external stresses, so if you plan to do that, somewhere forgiving and isolated would be the best bet.
Or you can build a society where you try to conquer the world. Or create technological marvels. Or maybe you want to try for specific ethical situations - build a matriarchy, or a Logan's Run "kill the adults" situation, or explore whether a democracy can work before the invention of writing. Or build a new village with fresh cultural rules in the ruins of your old, self-destructed empire...
I think this sounds very interesting, and I'm going to think about it some more.