Neat!

It would be nice to have the option to focus on a single content. It's much easier to learn things if you can go back and repeat, but repetition is prohibitive if you have to do the whole world again.

As a small comment, I went to click on a flag on mobile to see if I could see it bigger, and the name of the file came up, with the country's two-letter code, giving away the answer. I'd make it so the flag doesn't respond to touch/mouse events.