I have yet found a satisfactory way to apply a fixed background image to a page for mobile. For some performance reason, as I understand it, a fixed image for mobile is a dancing unicorn. Which has so far eluded me.
I’d like to implement it to match the desktop, but I’m not going to jump through brittle hoops to achieve it. Something will change in the technology landscape that renders the hack moot.
I even considered page scroll position changing. Probably the ultimate hack. But I dislike hacks and also magic numbers.