COLL_SIDE ={
         MD_NONE = 0, 
 	     MD_RIGHT = 1,
	     MD_LEFT = 2,
 	     MD_UP = 3,
 	     MD_TOPRIGHT = 4, 
 	     MD_TOPLEFT = 5, 
 	     MD_DOWN = 6, 
 	     MD_BOTTOMRIGHT = 7,
 	     MD_BOTTOMLEFT = 8
}