http://ee-flow-extra.instance-proxy.wmflabs.org/wiki/Special:UserLogin in Firefox and Chromium. But the kss.doc is fine, so it's some interaction with ResourceLoader and/or the CSS in other modules. I just noticed the background color doesn't darken on active, as if  &:active { background: shade(@bgColor, 20%); } isn't working. According to my [Insert Agora buttons] generator a page like http://ee-flow-extra.instance-proxy.wmflabs.org/wiki/Main_Page doesn't load other UI classes, so I'm not sure what's going on. I'll look at it some more tonight.