HypersomniacLive: Someone's fiddling with it, changing the css every now and then, for most part of the day. I've just added my own, as I find the new font horrendous to read.
Pajama: How do you do this? I'm finding the new font awful - terribly hard to read.
EDIT - just changed the settings in Firefox and am now back to a readable font but would still be interested in how to add my chosen font via css. Thanks.
I have Firefox installed in another account where I sometimes do cross-browser testing, and last I checked about personal stylesheets for Firefox I didn't find native support for that. Regardless of native support there is likely an extension available for applying CSS to visited pages.
I use Safari and it has basic support for stylesheets, meaning I can choose one file and it's applied to every visited page. That's in its "Advanced" panel of its preferences. Also there is the option to show the "Develop" menu which also enables "Inspect Element" with secondary-click (such as Control-click).
For the stylesheet I have noticed many of GOG's pages have in the <html> element a rather unique attribute, for which I use the attribute selector:
[ng-app="gog"]
For the
forums, that attribute doesn't seem to be included in the <html>. However the <body> element for the forum pages seem to consistently have the class "page_forum" so I use that as part of CSS selectors. I tested the following CSS with success. (It has two selectors separated by a comma.)
[ng-app="gog"] body,.page_forum{font-family:-apple-system,"Helvetica Neue",sans-serif!important}
Both selectors targets the <body> element because the font-family is set for that element in GOG's stylesheets. However, the font-family set for the body simply becomes a default inherited by other elements inside the <body>, which means it won't have any affect on an element which has the property directly specified for it. Another selector would need to be added override if that happens, by directly selecting that element.
BTW, both -apple-system and "Helvetica Neue" have more font-weight values than just normal and bold, though the former seems to be smaller for font-size and the latter more narrow. Picking a font-family like that gives me more options and so I end up using just one font instead of a mixture. (And of course, the -apple-system value is for only macOS, and perhaps only Safari.) Keep in mind that usually only the first font-family is what is used, except for when a character doesn't exist in it, which makes the other font-family values fallbacks, just in case.
EDIT: IIRC, Internet Explorer also has a preference setting for choosing a file as a stylesheet. Perhaps these default browsers for the operating systems have such a setting for accessibility reasons? Such as acceptance for government use? Might be why I haven't found the same settings in other browsers (Firefox, Chrome, etc.), though it seems to me they all have an extension system (which I don't use or test because extensions or plug-ins can't be reliably expected as installed).