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HTML5 is a great environment for building user interfaces.
You can famously build your page using the most basic text editor,
and odds are, whatever platform you happen to be using has a handy
renderer (or three) available: a browser.
It's easy to use HTML5 to configure and compose objects,
but you can only choose from the short list of built-in elements.
There are many wonderful tools in the world to extend what HTML5
can do, but they are all a little different. What if we could
all just extend HTML5 the same way: by making more elements.
This is exactly what Custom Elements are about.
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