Porting multi-z support updates.

code/modules/mob/dead/observer/observer.dm

@@ -17,6 +17,7 @@ GLOBAL_VAR_INIT(observer_default_invisibility, INVISIBILITY_OBSERVER)
 	see_in_dark = 100
 	invisibility = INVISIBILITY_OBSERVER
 	hud_type = /datum/hud/ghost
+	movement_type = GROUND | FLYING
 	var/can_reenter_corpse
 	var/can_reenter_round = TRUE
 	var/datum/hud/living/carbon/hud = null // hud

code/modules/mob/dead/observer/observer_movement.dm

@@ -0,0 +1,2 @@
+/mob/dead/observer/canZMove(direction, turf/target)
+	return TRUE

code/modules/mob/living/living.dm

@@ -40,6 +40,16 @@
 	QDEL_LIST(diseases)
 	return ..()
 
+/mob/living/onZImpact(turf/T, levels)
+	if(!isgroundlessturf(T))
+		ZImpactDamage(T, levels)
+	return ..()
+
+/mob/living/proc/ZImpactDamage(turf/T, levels)
+	visible_message("<span class='danger'>[src] crashes into [T] with a sickening noise!</span>")
+	adjustBruteLoss((levels * 5) ** 1.5)
+	Knockdown(levels * 50)
+
 /mob/living/proc/OpenCraftingMenu()
 	return
 

code/modules/mob/living/living_movement.dm

@@ -32,4 +32,7 @@
 		if(drag_slowdown && L.lying && !L.buckled && grab_state < GRAB_AGGRESSIVE)
 			add_movespeed_modifier(MOVESPEED_ID_PRONE_DRAGGING, multiplicative_slowdown = PULL_PRONE_SLOWDOWN)
 			return
-	remove_movespeed_modifier(MOVESPEED_ID_PRONE_DRAGGING)
+	remove_movespeed_modifier(MOVESPEED_ID_PRONE_DRAGGING)
+
+/mob/living/canZMove(dir, turf/target)
+	return can_zTravel(target, dir) && (movement_type & FLYING)

code/modules/mob/mob_movement.dm

@@ -370,3 +370,35 @@
 	if(hud_used && hud_used.static_inventory)
 		for(var/obj/screen/mov_intent/selector in hud_used.static_inventory)
 			selector.update_icon(src)
+
+/mob/verb/up()
+	set name = "Move Upwards"
+	set category = "IC"
+
+	if(zMove(UP, TRUE))
+		to_chat(src, "<span class='notice'>You move upwards.</span>")
+
+/mob/verb/down()
+	set name = "Move Down"
+	set category = "IC"
+
+	if(zMove(DOWN, TRUE))
+		to_chat(src, "<span class='notice'>You move down.</span>")
+
+/mob/proc/zMove(dir, feedback = FALSE)
+	if(dir != UP && dir != DOWN)
+		return FALSE
+	var/turf/target = get_step_multiz(src, dir)
+	if(!target)
+		if(feedback)
+			to_chat(src, "<span class='warning'>There's nothing in that direction!</span>")
+		return FALSE
+	if(!canZMove(dir, target))
+		if(feedback)
+			to_chat(src, "<span class='warning'>You couldn't move there!</span>")
+		return FALSE
+	forceMove(target)
+	return TRUE
+
+/mob/proc/canZMove(direction, turf/target)
+	return FALSE