Best way to debug any program is to add output statements.
Putting a <p> on page for debugging with <div> parent allowing scrolling.
HTML lines 40-42
CSS lines 22-26
JS lines 31, 35, 413, 422-423, 645-648, 759-761, 785-787
I change 31 to true to use.
I use click on paragraph that doesn't change to toggle on or off in my current program I'm debugging. Also note, this was my first web program and as such has tons of things I would change, if I started today. I been programming for 44 years explaining it's complexity.