anchor.diff:  The theme is driven by a YAML-based configuration file.
   This document explains how the theming system works, how to define a custom theme and how to enable the theme when running Asciidoctor PDF.
   
  +toc::[]
  +
   == Language Overview
   
   The theme language in Asciidoctor PDF is based on the http://en.wikipedia.org/wiki/YAML[YAML] data format and incorporates many concepts from CSS and SASS.
  
positive.code: = Asciidoctor PDF Theming Guide
  Dan Allen <https://github.com/mojavelinux>
  :toc: preamble
  :icons: font
  :idprefix:
  :idseparator: -
  
negative.code: 
  A theme (or style) is described in a YAML-based data format and stored in a dedicated theme file.
  YAML is a human-friendly data format that resembles CSS and helps to describe the theme.
  The theme language adds some extra features to YAML, such as variables, basic math, measurements and color values.
  These enhancements will be explained in detail in later sections.
  
  The theme file must be named _<name>-theme.yml_, where `<name>` is the name of the theme.
  