Personally… I’ve never done this. But I did come across someone a couple months ago who did this.
This is the page he pointed out to me.
And… hmm - interesting because at the bottom of that page it says… “Custom Elements with Shadow DOM”.
This - is reference to another post I did.
Now the fun part… trying to figure out how to make a straight line go diagonal.
I think this will be an html5 solution only - and will fail on html4 or below.