In reality, your css file size is most likely not going to be any type of bottle neck in website performance anyways. In my experience, browser side javascript

In reality, your css file size is most likely not going to be any type of bottle neck in website performance anyways. In my experience, browser side javascript is always the biggest render blocking issue with all the on-the-fly dom manipulation it might entail. Viewport specific css usually adds some kilobytes, a few hundred at most but the browser tends to be relatively swift about those as long as you don't use a lot of stuff like transitions or wildcard selectors on a broad spectrum.