Nebula is a WordPress theme framework that focuses on enhancing development. The core features of Nebula make it a powerful tool for designing, developing, and analyzing WordPress websites consistently, yet its deliberately uncomplicated code syntax also serves as a learning resource for programmers themselves.
Splitting this up from #1830 to give it its own issue.
Custom Selectors:
https://cssdb.org/#custom-selectors
This has been in stage 1 for a long time.