How to make popup scroll only in mobile browsers?

Question

css

I have a popop with a certain height. On a mobile device, the screen is small and therefore the popup pops out of the screen, how to make the popup scroll only on mobile phones, or so that you can press it with your finger and pull out the invisible part from behind the screen?

Answer 1

.popup{
position: fixed;
top: 20px;
left: 20px;
right: 20px;
bottom: 20px;
}

.popup_sub{
height: 100%;
overflow: auto;
}

redefine popup styles by media query to what is written above.