Hi, I'm the author of the course. Sorry the site isn't cooperating with your browser. I tested it fairly thoroughly on all browsers when I launched it, but that was 3 years ago. It's entirely possible Firefox may have deprecated some of the more obscure JS I used since then.
If you email me the details of the bug(s) you're running into to hello@vimvalley.com I can try to get them fixed. Otherwise if you're not averse to Chrome everything should work fine with Chrome on Linux.
If you email me the details of the bug(s) you're running into to hello@vimvalley.com I can try to get them fixed. Otherwise if you're not averse to Chrome everything should work fine with Chrome on Linux.