i thought this would be easy, but stumped.
i'm making a modal settings popup, and for the mobile version, i'm just keeping it simple for those with smaller screens. so, since i now want the whole screen to scroll, including the modal, it seems like the background "cover" i can only set to 100 of the viewport, not the actual height of the entire page (i.e. cover everything down to the end of the footer).
i think the secret was in this answer, but that evernote is since gone. seems like the answer starts with setting the body to 100%... but... then what?
please, go to the 2nd page - "my page" - the modal view should be visible. then, if you preview it, click the gear icon to get the modal to show. again, this is only for the mobile view: