"Next project" page load animation

Hi! I love the page loadings that Pentagram use on their case study pages. I have tried to reach the same result, but I can´t pull it off.
Would someone be interested in giving it a go? it´s a nice touch from one of the best branding agencies in the world.
Here´s the link, just go to the bottom of the page and you will see what I mean Channel 5

Here is my public share link: LINK
(how to access public share link)