With SASS and it's SCSS language I can create a much more dynamic CSS experience where your pages can even call and render dynamic changes sitewide if need be. Variables, user skins, interface per device format, all coded then compiled each page call by a PHP library I add to the php page call.

Here's a quick tutorial on what SASS and SCSS are if you are new to this CSS flexibility I can create for you.
SASS VS SCSS on DEV.TO.