Where may I find a reference scheme for GNOME 3 theming (e.g. Adwaita)?

I upgraded to Fedora 21, which spotlights GNOME 3.14 (plus the relevant GTK+ material). Unfortunately it seems that this particular update mangles a lot of my older themes, written for now-aging versions of GNOME 3. Where previously they may have squeaked by, they now look a little out-of-place. I don't presume to re-invent the wheel: I would be very happy to take a pre-existing CSS template (e.g. the default Adwaita 3.14 spec) and tweak it here and there to my liking; there will be no fancy flying. Imagine the hair I tore out when I peeked at /usr/share/themes/Adwaita/gtk-3.0/gtk.css: /* Adwaita is the default theme of GTK+ 3, this file is not used */ That puts me in a pickle. I lack the Google-fu to dig the documentation up about where this might be (worse, I have a gut feeling this is something implicitly obvious to GNOME people that I have been missing out on), and for some reason the GNOME developer website resists my attempts at researching their theming specification. In short, I'd like to find a virgin theme specification for GNOME 3.14, assuming one is extant. How may I do this, or how may I modify my approach?