Can't open in Firefox - images can't load

[Erik-k]

I am using Firefox 114.0.1 on Windows 10, desktop. I downloaded the whole git repo as a .zip and unpacked it, and when I open index.html from my file explorer, it displays the GUI correctly in my browser but in the center box it says, "Oh no! For some reason, we could not load all of the images required for game play. Please check your internet connection, and refresh the page."

I also cannot display the maptest.html. It simply shows a "broken image" icon in firefox.