A little research will be needed to see if the parallax scroll can be accomplished on mobile devices. I also took note of some 'jank' when the initial scroll takes place on mobile - it looks as if the "cover" background images are shifting some when the page begins to move. It's possible that this is due to the removal of the address bar once the page begins to scroll, changing the height of the viewport and thus the images are adjusting to fit.
Looks like this is mostly an issue with browser capabilities. Safari and FireFox do not presently support the animation-timeline property. I’ll have to look at a javascript pollyfill in order for it to work.
A little research will be needed to see if the parallax scroll can be accomplished on mobile devices. I also took note of some 'jank' when the initial scroll takes place on mobile - it looks as if the "cover" background images are shifting some when the page begins to move. It's possible that this is due to the removal of the address bar once the page begins to scroll, changing the height of the viewport and thus the images are adjusting to fit.