Downfall is a story game about creating and destroying a culture with a tragic flaw. During the creation portion, you choose a characteristic that is going to be the defining aspect of this new society… and is going to lead to its ruin.
The world-building portion is extremely satisfying — Sam Ashwell’s post gives a good overview of the general concept and functionality here.
In the session I played recently, we started with the flaw of Egalitarianism and a couple of related images (water, lakes, towers), and fairly soon had sketched out Titan Prime, a colony of turrets on an otherwise inhospitable moon. The original colonists had come from Earth generations before, but further ships never arrived, and the colony was now operating more or less independently, recycling all of its water and conserving its resources.
In the next stage of world-building, we established traditions of public and private fashion (everyone always wore uniforms in public); funerals (people were dehydrated for their water, then buried anonymously); justice (judge and jury roles were assigned by lottery, though once you’d been lottery-drafted you did receive some training); family (children were always fostered to someone other than a birth parent); and relationships (there was a complex system to make sure that you didn’t date your birth-sister even despite the fostering scenario). This is a fairly detailed place to get to on a half hour or so of gameplay, and I could easily imagine blending this with other campaign styles, or going over to a game of Microscope here to flesh out the historical events around the story.
The play of actual scenes, I found less tightly constructed.