Oh man, what's old is new again! I remember using spritesmith [0] to handle a big UI icons spritesheet. Even animated a few of these in the same way! (Though using background-position, a fixed size, and some javascript to change a class name once per frame.)
graypegg|7 days ago
[0] https://github.com/twolfson/grunt-spritesmith
Minor49er|7 days ago