Re: [mediaqueries4] Media queries for viewport positions

I see this being used in conjunction with position:sticky.

It's common for a header to change state once it becomes sticky, or at some
other point in the page. Google+ is doing this, for instance.

Something like:

@media (scroll-top-min: 300px) {
  /* change stuff, perhaps with transition */
}

would reduce the need for a scroll event (which doesn't work well on
mobile).