mouse move effect on full height and width in one pager

i am pretty new to the coding-world. I'm doing a small web project. I wanna do a one pager, that start with a full width and height mouse move effect (I've done this one: https://www.superhi.com/video/barron-webster). On the next stepp of the pager should be text, pictures etc.

The problem: if i have the height and width on 100% the java script ignore this and still uses the whole page and not only the viewport and the first "slide".

hopefully my problem is clear! Thank you for your answers.

i attached a picture: the colorful section is my start page. if i click on that i want to go down to the content page.enter image description here