How to make popup closing cross stuck to the screen when scrolling?

Question

css

There is a code - https://codepen.io/w0leg/pen/NWGMGQV
Please tell me how to make the popup closing cross stick to the screen when scrolling?
Something with position: sticky; does not exceed (((

Answer 1

Sticky works, the element must be positioned at the beginning as it sticks.
PS: at first I thought that overflow:hidden interfered with the footcloth of your code, but this is not so. However, please note that the stickypack does not work inside a block with overflow:hidden.