Codepen does not render React and plain DOM element

What am i doing wrong?

in the Codepen html window i have:

<div id="app"></app>

<hr style="background-color:red;height:1px" />
This should render regardless of React, it is outside the mount point.

Codepen here:

You’re accidentally closing your div tag with an app tag.

got it, sorry about that… fixed !

All good, cool tunes :ok_hand: