exterior : 
x,z in (-20..+20) visual horizon
x,z in (-18..+18) avatar roaming area
x,z in (-10..0)   castle

wallzp: x in [12+-7]=[5..19], z=5


x=20                                                                 x=-10
----------------------------- z=+20 --------------------------------------
					|
					|
		M			| wallxp: z in [4.8,19.8], x=5.2
					|
					|
----------E----|(5.2,5.0)
 wallzp
		   E@(7,5)
											Z+
											|
											|
z=0						X+_________(0,0).-------------------------------------
												|
												|
												|
                                    |
												|
												|
												|
												|					C
												|
												|
												|
												|
---------------------------- z=-10 ------------------E--------------------
x=20                                                                 x=-10


z=-20---------------------------------------------------------------------

