a few more changes related to map (#18557)

* we got a thing

* use flags

* makes it betterer

code/__defines/turfs.dm

@@ -8,6 +8,7 @@
 #define TURF_HAS_CORNERS        128
 #define TURF_IS_FRAGILE         256
 #define TURF_ACID_IMMUNE        512
+#define TURF_UNSHIELDABLE       1024
 // The 0x800000 is blocked by INITIALIZED, do NOT use it!
 
 //Used for floor/wall smoothing

code/game/objects/micro_structures.dm

@@ -139,7 +139,7 @@ GLOBAL_LIST_EMPTY(micro_tunnels)
 				if(!destinations.len)
 					to_chat(user, span_warning("There are no other tunnels connected to this one!"))
 					return
-				else if(destinations.len == 1)
+				else if(destinations.len == 1 || random)
 					choice = pick(destinations)
 				else
 					choice = tgui_input_list(user, "Where would you like to go?", "Pick a tunnel", destinations)

code/game/turfs/simulated/nanogoop.dm

@@ -226,6 +226,7 @@ GLOBAL_LIST_BOILERPLATE(nanite_turfs, /turf/simulated/floor/water/digestive_enzy
 			nutrients += how_much
 			targetcarbon.mind?.vore_death = TRUE
 			GLOB.prey_digested_roundstat++
+			targetcarbon.ghostize() //prevent runtimes
 			qdel(targetcarbon)	//glorp
 			return
 		targetcarbon.adjustFireLoss(damage)

code/modules/shieldgen/shield_gen_external.dm

@@ -20,7 +20,7 @@
 	for (var/x_offset = -field_radius; x_offset <= field_radius; x_offset++)
 		for (var/y_offset = -field_radius; y_offset <= field_radius; y_offset++)
 			T = locate(gen_turf.x + x_offset, gen_turf.y + y_offset, gen_turf.z)
-			if (is_type_in_list(T,GLOB.external_shield_gen_blockedturfs))
+			if (is_type_in_list(T,GLOB.external_shield_gen_blockedturfs) && !(T.flags & TURF_UNSHIELDABLE))
 				//check neighbors of T
 				for(var/i in orange(1, T))
 					if(istype(i, /turf/simulated) && !is_type_in_list(i,GLOB.external_shield_gen_blockedturfs))