Ask HN: How to author animation like today's Google Doodle?

Today's (2011-05-11) Google Doodle is an elegant animation in honor of Martha Graham.

The source of the animation is some JavaScript and a large .png sprite: http://www.google.com/logos/2011/graham11-hp-sprite.png

What kinds of tools are used to create animations like this?

(I assume this was made by a tool or framework, but I guess there's always a chance that this was lovingly constructed by hand.)