Mobile-first solution using flexbox

Really nice job on this project. I also used absolute for getting the pop-up to work. It looks like your solution scales properly when the screen size changes, so I don't see any problem with it being absolutely positioned since it works and displays correctly.

As far as whether to use h1 or img tag, I think that using an img tag, like you did, is better since an h1 tag is meant to be used for actual text. And you have the alt text for the image, so that takes care of the accessibility for the image. On a full website or app you would probably have an h1 somewhere else on the screen, but since this project is just a component I wouldn't worry about the h1 warning.

Also really nice job making the buttons focusable and keyboard accessible!