http://codepen.io/ryuran/pen/rrKNqL same without body:before.
css background only
Very smart. Took me a few minutes to figure out what you'd done. I like it!
Clever. If you add a second background with the $scroller-color you can have the full bar when you scroll to the end of the article. See: https://codepen.io/ObjectifMars/pen/qRZeLb .
Need to know how to enable it? Go here.