public void select(int x, int y)
   {
      if (x < 0 || y < 0)
      {
         s=null;
         a=null;
      }
      else
      {
         this.x = x;
         this.y = y;
         s = SugarPanel.getSugarGrid()[x][y];
         a = SugarPanel.getAgentGrid()[x][y];
      }
      update();
   }