anchor.diff:  type
     IMessage = interface
       function GetTag : integer;
  +    function GetData : variant;
       property tag : integer read GetTag;
  +    property data : variant read GetData;
     end;
     IActor = interface (IVorTask)
       function Send( msg : IMessage ):boolean;
  
positive.code:     constructor Create;
      procedure Invoke( cmd : string );
      procedure Clear;
      function Send( msg : IMessage ):boolean; override;
      procedure Draw; override;
      destructor Destroy; override;
    end;
  
negative.code:     end;
  
  procedure TWorld.Step;
    var a : IActor;
    begin
      HandleKeys;
      for a in self.children do
  