It differs from the Nokogiri tutorial on manipulating XML in that it shows how to do the most common operations on HTML rather than XML. And it shows how to do each operation using CSS and XML so you can choose your preferred syntax. It's been popular...
I propose this would be a good addition to the tutorial docs, but I'm not sure where it would should be parked.
If the community thinks this is a good idea, I'm happy to create a pull request and/or extend some Wiki entry. Just let me know if and where...
Best,
- ff
(P.S. my Pokemon Go nickname is 'robogiri', which I *hope* means something like "Robot Saw". Regardless, it was inspired by Nokogiri...)