What is the Google Gravity tool?

The Google Gravity tool can refer to one of several different projects, such as the one from Mr. Doob that shows the Google home screen, and then has all of the different links, the Google logo and the search bar fall to the ground. Another tool is from elgooG that features the same gimmick, but with everything reversed.

A similar tool from Mr. Doob, called Google Space, has all of the links, logos and search bars from the Google home page float around the screen as if there was no gravity. Anti-Gravity Google has all of the tools on the Google home page fall to the ground, but then bounce back up as if there was a very low amount of gravity.