There are HTML syntax/coding errors you should be aware of and address.
Since copy/paste from codepen you can ignore the first warning and first two errors.
Codepen provides validators for HTML, CSS and JS. Click on the chevron in the upper right of each section and then click on the respective ‘Analyze’ link.
The one for CSS is good. Use it and address the issue(s).
(The one for HTML misses things which is why I recommend W3C)
Do not use the <br> element to force line breaks or spacing. That’s what CSS is for.