In a not too distant future, the descendants of Earth have built their own worlds which to thrive on. By making numerous orbital habitats, the ancestors created living space far more vast than a singular habitable planet.
Scattered across the solar system, this swarm of worlds holds host to numerous civilizations who have long since deviated from the ancient human form. Where evolution has accelerated due to genetic modification and travel between these scattered worlds is commonplace. The know how to making super structures was lost in the past four centuries and modern civilization has rebuilt since than using primitive technologies. While travelling between the many worlds of our fugue is common place, the vast energy needs and scale of industry needed for making mega structures simply is not there.
Only recently have coherent, stable polities emerged. Yet even these polities, some with ancient histories dating back millennia, others a blank slate- have rebuilt their industries and have given birth to new generations of beings who desire to forge a new order, world by world.
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In short, it's a sandbox sci-fi NRP, except everything you have on the interstellar scale exists within a a swarm of many "tiny" worlds in orbit of a single star. Much of the same custom geography exists here with world building mega structures for your society to inhabit being the general idea.
Here's an article for anyone a bit confused on what I am even on about here:
earthsky.org/space/what-is-a-dyson-sp…