From the introduction:
In the Towers of the Sun, the Depths of Shadow, We Dance is a game set in a solarpunk future gone not-right; the solar-power-collecting-and-using nanotech that could have set the whole world free has instead made a greater division than ever between those with power (literally) and those without. Those who live in the high towers, whose hyper-efficient collectors and reflectors feed the nanotech batteries, can power all the machines that make their lives convenient with their own bodies.
Below them, in the shadows, live the Underdwellers, who cannot access nearly as much power by themselves; instead, they must spend their lives controlling what little power they get to its greatest effectiveness, and share power when there is something they need that is greater than what one of them can provide.