public boolean edit( int X, int Y ){
    boolean flag = super.edit(X,Y);
    if( !flag ){
      X -= LabyrinthDrawer.MARGIN;
      Y -= LabyrinthDrawer.MARGIN;
      int x = X/LabyrinthDrawer.CELL_SIZE;
      int y = Y/LabyrinthDrawer.CELL_SIZE;
      if( 0<=x && x<LabyrinthDrawer.DIMENSION && 0<=y && y<LabyrinthDrawer.DIMENSION ){
        structure[x][y] ^= (1 << 4);
        flag = true;
      }else{
        flag = false;
      }
    }
    return flag;
  }