From the Overview
Underbelly 8128 is a role-playing game about a roving city-state, a fantasy metropolis constantly moving from one place to another. One of many thousands, collectively known as the Kinetopolis Archipelago.
The people in the cities lead mostly cozy and comfortable lives, blissfully unaware of what it takes to keep the kinetopoleis moving. This game is not about those people. This game is about the people in the dark, cramped, dangerous mechanical underbellies of the cities, slaving away at the smoking furnaces and rattling conveyor belts.
The society these people live in is egalitarian and anarchist. It is the only life they know, but myths about the world in the Upper City abound. A world of riches and cheer beyond their grasp. Revolution is simmering, but never brought to a boil, as the various factions of the Underbelly are unable to form a united front or come up with an effective strategy. It is up to the player characters to bring change.