It feels like there's one of these "doesn't work on FF" threads any time there's a post about a halfway interesting web app.
Intentional or not, they really contribute (in my mind at least) to the overall perception that Firefox is truly dead. Nobody even tests for it anymore, or worse, accepts that it's fine to be broken on FF.
Counterpoint: I use Firefox with every privacy setting maximized and several extensions installed, and I can't remember the last time I had an issue with something posted here. This game works fine for me as well.
The only apps that are noticeably worse in Firefox for me are Google Docs and Google Meet.
I think part of the reason nobody tests for it anymore is just because web standards have largely gotten so good. I don't often test in FireFox these days myself largely in part because it just hasn't been a problem in years.
I'm old enough to remember the days when every change I made I had to roll through multiple versions of IE all the way back to 6, and different things would be broken in different versions.
Transparent PNGs using CSS filter:progid:DXImageTransform.Microsoft.AlphaImageLoader is my shudder. Flat design would have made life so much easier back then.
I feel first we need to validate the original premise that there's something wrong with this game in Firefox.
I'm running Firefox, with containers enabled, with ublock origins (and as such "somewhat privacy conscious over and above the defaults"), and this works fine for me.
There could be any number of things that cause an individual issue, which may or may not be related to Firefox itself :-/
Resist Fingerprinting was enabled. I updated my comment to note that.
BTW, Resist Fingerprinting's main impact (for me) has been to increase triggering of "Click and Hold to prove you are not a bot" on sites relying on fingerprinting as an anti-bot measure (Drupal, Walmart, Kickstarter). On some of those, the developer doesn't even realise that measure can trigger, and it triggers in a background XHR (Kickstarter does this sometimes).
This is still better than some other sites like Lowes and Fedex where the entire site (Lowes) or backend API (Fedex package tracking) simply errors due to an Akamai block without any option to prove yourself. For those, you pretty much just have to use another Firefox profile with fingerprinting allowed (or another website).
.. oh, and none of the stuff above is due to Firefox blocking anything (like in the situation of this game where you have to click in the URL bar on the image icon) it's entirely due to the setting working too well, and making the user suspiciously generic :)
Intentional or not, they really contribute (in my mind at least) to the overall perception that Firefox is truly dead. Nobody even tests for it anymore, or worse, accepts that it's fine to be broken on FF.