Why isn't code mirror defined?
So repl is telling me that code mirror didn't load even though I used the exact code from the code mirror website.
Don't worry if you don't understand, here is a simple template to help get you started
The issue is that your source code for code mirror is looking for a file inside of a folder called
lib which doesn't exist, so unless you actually copy the source code and put it into a file, you'll need to use the cdn script tag.
I think you need to put this in the head
<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.61.0/codemirror.min.js" integrity="sha512-LwxFyHyqmDdcint8dhTSHeJuI+uH5r/vrcGkxH4QhHGP8SpNaS9MVa1BxZRNTb1GPyLBAWrjbWpZTPGgtDgJOw==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>