The particular methods for making CSS backwards compatible are specific to the web, but the general problems faced by having user display preferences are not. Adding these features to native apps blows up your testing matrix there, too.

In many ways, it's even worse. I've got OS settings here for "increase contrast", "reduce transparency", "use grayscale", "invert colors", and (because areas of native windows can be translucent) even the desktop wallpaper comes into play.

I turned on dark-mode for testing my own app, and I had to turn it off because there's parts of Xcode where the contrast ratio is less than 1.1:1.0. The text is downright invisible. Obviously nobody at Apple would ever intentionally make software like that. They must have simply never thought to test with the same settings as I have.

https://pbs.twimg.com/media/D1kfN6SUcAEwWxq?format=png&name=...