This is pretty informative even to someone who's been doing CSS for years now. Always nice to visually see how something works. It would be nice to show what kind of browser support each of these items have.

Is all this stuff supported in modern browsers? It would be great if it showed browser compatibility for whichever one is selected.

Peter-Paul Koch (ppk) has a good guide to selector support in desktop browsers:

http://www.quirksmode.org/css/contents.html#CSS3

Not sure if there is a comparable mobile one.

Thanks for not using Bootstrap. Refreshing feel.

this is one of those so-simple-yet-effective learning techniques that is obvious in retrospective :)