The idea is very simple, the code is very concise, the effect is good, and it is quite useful (IE naturally does not recognize this kind of advanced stuff).
* {outline: 2px dotted red}
* * { outline: 2px dotted green }
* * * { outline: 2px dotted orange }
* * * * { outline: 2px dotted blue }
* * * * * { outline: 1px solid red }
* * * * * * { outline: 1px solid green }
* * * * * * * { outline: 1px solid orange }
* * * * * * * { outline: 1px solid blue }
It’s easy to understand, using outlines of different colors and different line types to mark hierarchical relationships.