It astounds me that in 2024 there’s no canonical way to select which CSS to use for a web browser on a phone screen. You have to guess at how many CSS pixels wide your target device is. If next year’s device is any larger than a hardcoded threshold, they may get your desktop layout instead.
I know there are people who’ve made their careers out of memorizing all the edge cases of this monstrosity. Those are lifetimes lost to toil because no one can agree on an official way to look nice on a cell phone, or the one true way to center an image. It’s madness.