Shafted (#2704)

Ladders now have proper open-space shafts. Their sprite has been edited to remove the faux-hole, and also the down sprite is now at the same vertical pixel adjustment as the up sprite, so it looks kinda like they connect.

For security's sake, you can no longer fall down an openspace if there is a ladder on the openspace tile. Strangelly enough there was already code for not falling down if there was a ladder below you.

Added flight to some simple mobs that had been excluded from Alberyk's initial runthrough (parrots, bees, bats, and shades.)

The purpose of this PR is that you can now fly up ladder shafts.

code/modules/mob/living/simple_animal/bees.dm

@@ -252,6 +252,14 @@
 /mob/living/simple_animal/bee/attempt_pull(var/mob/living/grabber)
 	return attempt_grab(grabber)
 
+/mob/living/simple_animal/bee/can_fall()
+	return FALSE
+
+/mob/living/simple_animal/bee/can_ztravel()
+	return TRUE
+
+/mob/living/simple_animal/bee/CanAvoidGravity()
+	return TRUE
 
 //Bee for spawning as a hostile mob, it wont fade without a hive
 /mob/living/simple_animal/bee/standalone

code/modules/mob/living/simple_animal/hostile/bat.dm

@@ -88,3 +88,12 @@
 /mob/living/simple_animal/hostile/scarybat/cult/Life()
 	..()
 	check_horde()
+
+/mob/living/simple_animal/hostile/scarybat/can_fall()
+	return FALSE
+
+/mob/living/simple_animal/hostile/scarybat/can_ztravel()
+	return TRUE
+
+/mob/living/simple_animal/hostile/scarybat/CanAvoidGravity()
+	return TRUE

code/modules/mob/living/simple_animal/hostile/faithless.dm

@@ -89,3 +89,12 @@
 	. = ..()
 	for(var/spell in darkform_spells)
 		src.add_spell(new spell, "const_spell_ready")
+
+/mob/living/simple_animal/hostile/faithless/can_fall()
+	return FALSE
+
+/mob/living/simple_animal/hostile/faithless/can_ztravel()
+	return TRUE
+
+/mob/living/simple_animal/hostile/faithless/CanAvoidGravity()
+	return TRUE

code/modules/mob/living/simple_animal/shade.dm

@@ -51,3 +51,12 @@
 				ghostize()
 		qdel(src)
 		return
+
+/mob/living/simple_animal/shade/can_fall()
+	return FALSE
+
+/mob/living/simple_animal/shade/can_ztravel()
+	return TRUE
+
+/mob/living/simple_animal/shade/CanAvoidGravity()
+	return TRUE