anchor.diff:  
   We'll cover more about math expressions in the next section.
   
  -=== Math Expressions & Functions
  +=== Math expressions & functions
   
   The theme language supports basic math operations to support calculated values.
   The following table lists the supported operations and the corresponding operator for each.
  
positive.code:     left: '{page-number} | {chapter-title}'
  ----
  
  == Applying a Theme
  
  PENDING
  
negative.code:   - Alignment (left, center, right, justify)
    - Color as hex string (e.g., #ffffff)
    - Image path
  * Number (integer or float) with optional units (default unit is points)
  * Array
    - Color as RGB array (e.g., [51, 51, 51])
    - Color CMYK array (e.g., [50, 100, 0, 0])
  