This page is used to create the loading indicator image. As old browsers and even new ones struggle with complex CSS animations like box-shadow, it's better to create a GIF from this animation and reference that. That's exactly what was done here. To change the loading indicator, record the animation and save it as GIF. I used https://www.screentogif.com/ for that. Reason to create our own loading indicator is that most indicator GIFs out there are not compatible with the GPL license.