Update: The JS on this site frequently crashes on a fully updated Linux Firefox browser. It's neat so I honestly would have paid, but it just freezes up during some of the later exercises.
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.
