HTML editor
If you’re mainly working on the HTML for a time–or the whole generator is HTML only–working in a smaller box that’s underneath the preview (so you can either see a lot of the preview or a lot of the HTML) is a little annoying. A button to swap the editors so you can have the HTML on the left would be cool.
Alternatively (may be more work, I don’t know)… Put the preview and REPL (“Tester”?) on the right side, as they’re both “live.” And put the code editors on the left side, as they’re both “code.” Then you could make either as big or small as you wanted. And if you don’t use the REPL much (like me) you can make that real small still.
Code text size
Personally I’d love the ability to make the text larger, independently of the whole page. I can use ctrl+
to make the whole page’s size larger or smaller, but I don’t want the preview to be larger, or the top buttons to be larger, etc. Just the code itself. /
Could be a nice accessibility feature.