Animated "Ticker" Style Page Border

Hello everyone! Is it possible to create an animated page border in Squarespace using custom CSS like this one on the global climate strike website? 

https://globalclimatestrike.net

Also, I'm having some trouble creating a regular page border around my entire site. I've input this code into the custom CSS area, and a border appears around the entire page, except for the top portion where the header area is. 

body {
     border: 14px;
     border-style: solid;
     border-color: #000000;
 }

Thank you in advance for your help with these questions!

Hello - I see this was a while ago. I'm curious if you received any feedback or how you solved this? I am interested in something similar - a CNN style news ticker scrolling across a bar on my site. thanks. 

Unfortunately I didn't, and haven't been able to figure it out. Would still love to know though!