Mimic scrolling functionality?

Hey guys, i’m trying to mimic the scrolling feature of this website: http://nylllon.com/
But i’m having a bit of trouble making content that’s not in the view hidden. I see that in their code, they have 2 wrappers for the columns, one that has the overflow:hidden and then one that just holds in the columns. I did this but there seems to be a little more than that going on…
How would you achieve hiding the content that’s not in view?
Here’s my code:

	width:1600px; // this will be handled with javascript