This page is an example of the flexibility of the mootools framework. Utilizing the different states of the dom, with the functions build right into the framework for easy access, one can create many effects like this one, and also interact using ajax and lots of other cool stuff.
Check out the Javascript code, and the CSS
Note:This does not work in all browsers so use at your own risk. I have haulted development of this with no particular time set to start again, or even ever start it again.
This page works best in Firefox.