Right… I had it working at some point, I guess :focus-within has some limitations. (This could be solved by :target-within, if browsers implement it someday)
I clicked the back button and that did not work (Chrome, desktop). Seems this demo has a ways to go yet. Not bad for an MVP!
Works fine mobile safari
Safari desktop shows always the first image ("The Donut Hole").
iOS Safari, the detail view worked for the first image I clicked on, but just gets stuck on the last image you closed out of. You can still scroll to a new image, but it won’t update to a newly clicked one.