> In 2127, after the Great Subsidence disaster, the surface was blanketed in deadly toxic dust and mutagenic radiation. Humanity huddled in a vast underground hive stitched together from the old subway network, bomb shelters, mines, and gigantic sewage pipes: the Rust City-States.
> The city-states are built in a **vertical shaft structure**:
> - **Top level, the Dome District**: Controlled by the old elite and new tech companies, it simulates a false blue sky and boasts clean hydroponic farms and holographic entertainment.
> - **Middle level, the Hive District**: Home to the vast working class, who keep the city-states' energy supply, powered by geothermal reactors, and air-circulation systems running as they toil day in and day out.
> - **Bottom level, the Rotsoil District**: A lawless zone overrun by mutant fungi and divided among gangs, with glowing rivers of polluted wastewater running through it.
> **Deadly threats**:
> - **Rust Disease**: An incurable condition in which organs become metal, caused by inhaling too much metallic dust.
> - **Hive Shedlings**: Humans mutated by radiation. Some retain their intelligence, while others become bloodthirsty monsters.
> - **The Silent Tide**: Periodic energy storms that surge from deeper caverns and burn out all unshielded electronic neural implants.
