http://leaverou.me/2011/01/styling-children-based-on-their-number-with-css3
Info from http://glazkov.com/2011/01/14/what-the-heck-is-shadow-dom/
(not just on pseudoelements)
No-Library (pure JS), HTML, CSS, JavaScript
An alternative, more concise solution than http://css-tricks.com/three-sided-border/
Testing box-shadow radii when spread is set (WebKit bug testcase)