I really question the value of using CSS in the examples. I find it a significant distraction for all but the fundamental features like <h1>, bold, etc.
The card style is cute, as are sliding switches, but they introduce unnecessary complexity. Even what should be simple changes result in digging substantial holes for obscure formating. I’ve no intention to devote mental resources to CSS.
My plan is to take the WiFi Mgr code and create a copy/paste for the declarations, then a couple of #includes which will all the feature to be easily “plugged in” to any ESP32 project. Having that capability presented in the ebook would be way more useful than CSS.