sweet half life routes:
									    normal route  -> shl_5 ---------------> shl_6 -> shl_7
									    |				  |				   
shl_training -> shl_0 -> shl_1 -> shl_2 -> shl_3 -> shl_4      			  |		 		   
								       	    |				  |			    
									    alien route  -> shl_4b -> shl_5b