OP here. Maybe this is what I should do for my example applications and the "Learn Ruby on Rails" book. Use mixins from either Bootstrap or Foundation in a CSS

OP here. Maybe this is what I should do for my example applications and the "Learn Ruby on Rails" book. Use mixins from either Bootstrap or Foundation in a CSS file so I can use my own semantic CSS classes in the application views and isolate my code from the front-end framework. Though it sounds like too much complexity to introduce to Rails beginners in the book.