Makes the singularity eat asteroids, adds a planetary z-level list with a helper that adds maps to it

code/__HELPERS/unsorted.dm

@@ -1453,3 +1453,7 @@ GLOBAL_PROTECT(valid_HTTPSGet)
 	var/temp = bitfield - ((bitfield>>1)&46811) - ((bitfield>>2)&37449) //0133333 and 0111111 respectively
 	temp = ((temp + (temp>>3))&29127) % 63	//070707
 	return temp
+
+//checks if a turf is in the planet z list.
+/proc/turf_z_is_planet(turf/T)
+	return GLOB.z_is_planet["[T.z]"]

code/game/turfs/simulated/floor/plating/asteroid.dm.rej

@@ -0,0 +1,14 @@
+diff a/code/game/turfs/simulated/floor/plating/asteroid.dm b/code/game/turfs/simulated/floor/plating/asteroid.dm	(rejected hunks)
+@@ -101,10 +101,9 @@
+ 	return
+ 
+ /turf/open/floor/plating/asteroid/singularity_act()
+-	if(!turf_z_is_planet(src))
+-		ChangeTurf(/turf/open/space)
+-	else
++	if(turf_z_is_planet(src))
+ 		return ..()
++	ChangeTurf(/turf/open/space)
+ 
+ /turf/open/floor/plating/asteroid/singularity_pull(S, current_size)
+ 	return

code/modules/mapping/mapping_helpers.dm

@@ -49,3 +49,21 @@
 /obj/effect/baseturf_helper/lava_land/surface
 	name = "lavaland baseturf editor"
 	baseturf = /turf/open/lava/smooth/lava_land_surface
+
+
+//Contains the list of planetary z-levels defined by the planet_z helper.
+GLOBAL_LIST_EMPTY(z_is_planet)
+
+/obj/effect/mapping_helpers/planet_z //adds the map it is on to the z_is_planet list
+	name = "planet z helper"
+	icon = 'icons/obj/items_and_weapons.dmi'
+	icon_state = "syndballoon"
+	layer = POINT_LAYER
+
+/obj/effect/mapping_helpers/planet_z/Initialize()
+	. = ..()
+	var/turf/T = get_turf(src)
+	if(!turf_z_is_planet(T))
+		GLOB.z_is_planet["[T.z]"] = list()
+	qdel(src)
+