[PTTG]

Originally Posted by tshiggins

It's basically a "smoke ring" setting with floating asteroid-slands.

https://en.m.wikipedia.org/wiki/The_Integral_Trees

It also reminds me of this computer game, although the game definitely has a "down":

https://www.worldsadrift.com/blog/welcome/

Thank you! I knew I read about the concept somewhere... thanks for the link.