anchor.diff:  
   
   abstract class Card {
  +  final String name;
     const Card();
   }
   
   class Character extends Card {
  -  final String character; 
  -  
  -  const Character._(this.character);
  +  const Character._(this.name);
     
     static final Character SCARLET =
         const Character._("SCARLET");
  
positive.code: }
  
  class Weapon extends Card {
    final String weapon;
    const Weapon._(this.weapon);
    static final Weapon KNIFE =
        const Weapon._("KNIFE");
    static final Weapon CANDLESTICK =
  
negative.code: }
  
  class Room extends Card {
    const Room._(this.name);
    
    static final Room HALL =
        const Room._("HALL");
  