[NikolaNovak]

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 :-/

[chungy]

Indeed, I have strict mode enabled, uBlock Origin, containers, and the game works completely fine.

[capitainenemo]

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 :)