Well, that seems to be some proprietary code, but the concept doesn't seem too difficult. I can think of two ways to do it, right off. Give me a while and I'll come up with a few more ways.
Put an overlay <div> on the page to start with, one that covers the main area of the page. Then use JS to "shrink" that overlay, moving its top left corner down and right over a period of time. Thus the content of the page is progressively revealed.
But I think we could refine that.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.