As BS student of CS at Math Department in Padua I made this interactive page which implements the described protocol for easily protecting weaker passwords

I think you can simply use preprocessors and write vanilla css as well, and using just a few preprocessor's features that could really help you maintaining your code (maybe variable). If you write on sass as you write in css, it will get compiled in the same way. If you find it too slow to compile, maybe you are using an high level compiler. There are native ones like http://sass-lang.com/libsass and i can't figure out lasting about 1 second to compile.