* ---------------------------------
		 *           *                             |
	   *                     *                         | 
       *                            *                      |
     *                                 *                   | 
    *                                    *                 |
   *  --------------- * *                  *               |
  *   |             *       *                *             |
 *    |           *           *               *            |
 *    d         *              *              *            D 
 *    |         *              *              *            |
  *   |           *           *              *             |
   *  |             *       *               *              |
    * ---------------- * *                 *               | 
     *                                   *                 |  
	*                             *                    | 
	    *                    *                         |
		*            *                             |
			*-----------------------------------