I'm still slightly uncomfortable with css being able to do anything more than positioning, coloring and fonts... and maybe hover selectors though I did abuse those severely when I found out about them.

Nevertheless, demos like this are pretty cool.

That is because the animation capabilities of CSS are still meant to be used for presentation purposes (like a cute response to mouse movement or a head bobbing around), rather than an all out game engine. The idea is still cute, but I freak that people will think this is the new way to design online games.