Much like how Jade is better than writing HTML, there are preprocessed languages for writing other languages. These include languages that compile into CSS, JS, and even specialized subsets of HTML for basic formatting. This book will not attempt to teach any of these to you because honestly, there are already great resources out there for learning all of them. However, it is worth mentioning these languages because Jade has a feature called filters that allows you to use several of them right inside your templates.