Exactly as I would do it if I were a 7yo. Speak what you will about the virtues of CSS and semantic markup, these things get in the way of having fun. And can be learned later.
I agree with you, but for shits and giggles, to modify this to be evangelist compliant, you could write this instead: Which isn't much more complicated, and makes it clearer what's going on. I wonder if there is a transpiler like Elm that could take a single file written in a simplified language and gave you an HTML5 compliant webpage? You could argue that all the XML-but-not-actually-XML crap in HTML (angle brackets…
Also, there's nothing XML-but-not-actually about HTML. Both HTML and XML are derived from SGML.