The balls gradually settle into the familiar blue-yellow-green-red color scheme of the Google logo. And depending on which browser you're using, they stir themselves up to welcome you back from another tab. Guess what: it works best with Chrome.
That seems to be because the balls rely on HTML5. Viewing the source for the page reveals what is, at least on my laptop, six full screens of code.
That's a labor of love, and I guess it should be: The one-off logo is evidentlya way for Google to celebrate its birthday. The actual anniversary of Google has spurred many questions before, especially when the company "reset" the date so it would coincide with an indexing benchmark.
All that's covered elsewhere, and exhaustively. My personal favorite explanation was when the company said it just likes to have cake at different times of the month.
For now, you can just poke around the page with your mouse while you wake up, and watch Google's recombinant party-balls settle down — before you put them back into a tizzy.
And if you'd like to review all of Google's Doodles — it's one-off logo tricks — then you're in luck, because the company isn't shy about compiling them for your review.