I don’t think I’ve seen this specific method used yet, but it seems like one of those super obvious techniques. This technique is not really anything new, it just combines two concepts that most CSS developers should be fairly well familiar with by now.
CSS sprites are a method for creating complex rollovers without using JavaScript.
CSS3 animations (or more accurately, CSS3 transitions) is a new feature that has been added to some newer browsers, most notably WebKit-based browsers like Chrome and Safari. Like sprites, CSS3 animations don’t require JavaScript.