anchor.diff:  important
       : IMPORTANT_SYM
       ;
  -    
  +/*    
   expr 
       : term ((WS+|WS* operator WS*) term)*
       ;
   
   term
  -    : unaryOperator?
  +    : additiveExpression
  +    | unaryOperator?
           (
                 NUMBER
               | PERCENTAGE
  
positive.code:     | PLUS
      ;  
      
  operator
      : SOLIDUS
      | COMMA
      ;
      
  
  hexColor
      : HASH
      ;
      
  function
      : IDENT LPAREN expr RPAREN
      ;
      
  // ==============================================================
  // LEXER
  //
  
negative.code:     ;
              
  ruleSet
      : selector (WS* COMMA WS* selector)* WS* 
        LBRACE 
          (WS* ruleSetElement)* 
        WS* RBRACE
      -> ^(RULESET ^(SELECTOR selector)+ ruleSetElement*)
      ;
      
  ruleSetElement
      : declaration
      | variableDef
      ;
  
  selector
  