How to change the purpose of the function (when clicked, return the original src)?

Question

css

There is a block in which there is a hidden block (modal window) in which there is an iframe, when the site loads, all iframes replace the original src with a 1px image for faster site loading.
- then the user clicks on the block > a modal window opens > the play button appears when clicked on which returns the original src for the iframe > the video starts.

Help remove the gap in the form of this button and reassign the function of assigning the original src iframe y click on the main block.

Everything is related to arrays as I understand it. The code is hard for me.

Link to codepen JS code with comment https://codepen.io/Agas007/pen/PoqOEqV

Answer 1

Because after #list1 there is no .ul1
To get to it, you need to go to the top level, and css can't do that.