The bugs in the background are fun to watch. They actually eat each other from time to time. Though it does seem to require some CPU power and got my fans to spin up a bit.
And yes, it's a huge cpu hog. But it will pause when you unfocus/hide the page.
[edit - yes - it says this at the bottom of the page!]
Anyway, I've made it so that the bitmaps are hidden when the animation is disabled, since they are the most likely candidate for making scrolling slow.