Connect DIV with line on hover over for responsive webpage

Hello guys,

This community has been most helpful over the years.

I hope that someone could help me upgrade a webpage that I’ve stated as a fun project some time ago but now I see value in upgrading to an actual webpage.

There are a couple of things in particular that I would appreciate if someone could help me with:
a) Advise on what would be the best approach to make it responsive (right now I use flex with EM margins set for the elements)
b) Create a hover over animation which shows a connecting line between 2 images/divs and be responsive.

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