I can't help myself, but for me this idea of "functional CSS" stands again the idea of cascading stylesheets. I cannot follow the criticism on semantic markup, because there's nothing bad about semantic, precise markup, except you are a designer and only care about visuals.<p>A core idea of CSS is nesting of expressions, and I've seen many usages of SASS/LESS which render to expressions such as ".body.active h2#primary" which just show the author did not understand how to write efficient and precise CSS queries.