Many fortnights ago, I foolishly thought writing a GTK3 theme from scratch would be easy. It was mostly CSS unlike GTK2. About 40 minutes in came a horrifying realization: there’s fundamentally (and definitively) no way to write a consistent theme that works reliably with every application. The minor upside was a working (and somewhat accessible) wireframe theme and a basic understanding of debugging. The end.
GTK_DEBUG=interactive firefox