Drag down to see the content below, up to see above. Total scroll height is 100% of the page and the bar will have an height equivalent to the portion of page y

Drag down to see the content below, up to see above. Total scroll height is 100% of the page and the bar will have an height equivalent to the portion of page you're seeing, allowing to predict from a simple glance how long a page is. I'd say it's quite beautiful in its functional simplicity.