How is this built? Is this built on d3.js? This reminded me of old flash style plugins which we don't see any more.

It's using Three.js[^1] with Photons[^2], and a number of other interesting libraries for calculation like satellite-js[^3].

[1]: https://github.com/mrdoob/three.js/

[2]: https://github.com/mkkellogg/Photons

[3]: https://github.com/shashwatak/satellite-js