I'd like to create a theme based on Adwaita.
I discovered that Adwaita no longer uses
cat /usr/share/themes/Adwaita/gtk-3.0/gtk.css /* Adwaita is now part of GTK+ 3, this file is no longer used */
I found the Adwaita source code on GitLab:
VERSION 3.24.10: https://gitlab.gnome.org/GNOME/gtk/tree/3.24.10/gtk/theme/Adwaita
(UPDATE: The "master" branch on GitLab may be "buggy" since it is in development. Instead, a more stable branch such as 3.24.10 should be used).
Therefore, I can download the source files from Gitlab and modify the included
*.scss files with the color changes I want.
Once I've made my changes, how do compile the source into a new theme, and deploy it on my machine?