This was excellent. I haven't been doing as much web development lately so this was a great reintroduction to stuff I haven't gotten to use. It reminds me of 15-20 years ago learning HTML for the first time.
$.02 on unregistered custom elements: I'm sure they have a place, but I'd exhaust every other option first and then consider using a div with a class. There's a place for creativity and a place for standards, and something that both people and software must read and understand is a better fit for standards.
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