Tropes in Use
Absent Aliens - Humanity has explored some of the galaxy and it turns out the truth isn't out there. There are no aliens, or at least, no intelligent ones. The focus of this genre struggle between human populations, and aliens could either help them resolve their differences or serve as a threat encouraging them to do so themselves.
Arcology – Imagine a skyscraper. Every five or so floors, there is an entire floor dedicated to the inner workings of the floors above it. This is called a deck. The deck level houses all power lines, plumbing mains and anything else that needs to work properly for life to be livable with all the modern conveniences. Now make the skyscraper cover the ground area of a small city or a large town and realize that the decks number in the triple digits. The name of the game here is self-sufficiency. Because such places are so insular and answer all of humanity's material needs, they are a great setting for a Wretched Hive masquerading as a Shining City, if not just playing the Layered Metropolis disgustingly straight.