anchor.diff:        constructor Create(etag: integer; edata:variant);
       end;
   
  -type
  +
     TActor = class (TVorunati<IMessage,void>, IActor)
       _active,           { wants update() }
       _alive,            { exists but not alive triggers gc }
  
positive.code: 
  
  type
    TWorld = class (TMorph)
      public
        procedure Step; override;
        procedure Draw; override;
        function Done : boolean;
      end;
  
  procedure TWorld.Step;
    var a : IActor;
    begin
      HandleKeys;
      for a in self.children do
        if a.active then a.Step;
      Draw;
  
negative.code:     function Send( msg : IMessage ):boolean; override;
    end;
  
  
    Point = object
      x, y : integer;
    end;
  