How do I change the size of this div? (content in div is not responding)

I am trying to change the size of the preview window, but when I edit the height using the id preview , the text is not affected. How do I make a window that can become a full screen like the one shown in the example given?

Here is my pen

Remove the height: 100px from the preview id selector. You currently are limiting the height to always be 100px. The default value is auto which will expand to the content inside it.

What I am trying to change is the height of the previewer. I’m not sure if I make sense, but I’d like to change the overall size of the previewer and make it smaller.

I understand. If you do what I said above, it will expand the preview to the full height of the content in the editor. I just looked at your project and you appear to have resolved the issue?

What height are you wanting the preview to be?

I was trying to make it a bit smaller than the height of the viewport. I’m not sure exactly.