Sorry for the nitpicking, but since it seemed awesome enough for me to go check on I figured I'd leave the link & name here:

"Dyson Sphere Program"

https://store.steampowered.com/app/1366540/Dyson_Sphere_Prog...

(I figured - how often are the author(s) going to get some traffic from HN? May as well make it count :) )

On a similar note, the Gigastructural Engineering & More mod for the space strategy game Stellaris adds a broad variety of fully visually modeled megastructures that sufficiently advanced space empires can build, ranging from academic theoreticals like Alderson disks to 'more gun' space combat uses like Death Stars to just-there-to-be-silly items like Discworld-style flat 'planets'.

If you like Tsutomu Nihei's megastructures and video games (specifically Half-Life 2 modding scene and old-school, retro-to-the-bone shooters), you should check out G String [1]. My 2020 GOTY hands down.

But an absolute go-to for lovers of virtual architecture is NaissanceE [2], which is free on Steam.

[1]: https://store.steampowered.com/app/1224600/G_String/

[2]: https://store.steampowered.com/app/265690/NaissanceE/