More HTML tips / tutorials please

I feel that small HTML puzzles tricks could be very helpful for non coder users.
Things like:

– setting the background of the scene (Verge3D with transparent background)
– execute code from annotation click
– connection HTML UI elements —> puzzles, even the basics (which file to modify, how does the basic bi-directional connection works in principle)

I’ve heard there will be an execute code direct from puzzles node in 3.4?
Maybe some real world examples accompanying it would be nice.