The Smilies in Gmail - Gtalk

Hey,

A lazy Saturday afternoon, chatting on Gmail with a couple of friends, and this interesting thing caught my attention. Strange that it had not caught my attention till now, but I decided to check out the way the smilies rotate. This is not rocket science, but I sure was impressed by the way it was done.
It is obvious that the rotation cannot be textual, and so I was looking at the presence of a GIF to do the job. However, I discovered this image replaced the actual text with this and this being the background images. The animation was achieved by using a setTimeOut and changing the -x-background-y-position style from 0 to 132 at regular intervals. Thats is how the image seems to rotate.
Now this is a pretty interesting way to achieve animation, given the fact that the animation has to be replayed when a user hovers the mouse on the smilies. Sure thing that GIFs to achieve would be a pain, specially the way animation is handled across Internet Explorer and Firefox !!