Zoom in - Zoom out problem on the Javascript Background

I want to apply a javascript background on my website. I found a ready one, but I recognize a problem on it. When you scrool with mouse on browser, zoom in or zoom out, it starts to look so strange. You can try it on your own from that demo link;

Demo

Also the html and css code of this animational background is in this link;

Link of HTML-CSS-Javascript of this demo

Can you help me, how can I prevent it from being zoomed in or zoomed out on a browser ?