Rewrites Atmospherics

code/ZAS/Atom.dm

@@ -1,34 +1,46 @@
 
 
 /atom/var/pressure_resistance = ONE_ATMOSPHERE
+/atom/var/can_atmos_pass = ATMOS_PASS_YES
 
-/atom/proc/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
-	//Purpose: Determines if the object (or airflow) can pass this atom.
-	//Called by: Movement, airflow.
-	//Inputs: The moving atom (optional), target turf, "height" and air group
-	//Outputs: Boolean if can pass.
+// Purpose: Determines if the object can pass this atom.
+// Called by: Movement.
+// Inputs: The moving atom, target turf.
+// Outputs: Boolean if can pass.
+// Airflow and ZAS zones now uses CanZASPass() instead of this proc.
+/atom/proc/CanPass(atom/movable/mover, turf/target)
+	return !density
 
-	return (!density || !height || air_group)
+// Purpose: Determines if airflow is allowed between T and loc.
+// Called by: Airflow.
+// Inputs: The turf the airflow is from, which may not be the same as loc. is_zone is for conditionally disallowing merging.
+// Outputs: Boolean if airflow can pass.
+/atom/proc/CanZASPass(turf/T, is_zone)
+	switch(can_atmos_pass)
+		if(ATMOS_PASS_DENSITY)
+			return !density
+		else
+			return can_atmos_pass
 
-/turf/CanPass(atom/movable/mover, turf/target, height=1.5,air_group=0)
-	if(!target) return 0
+/turf/can_atmos_pass = ATMOS_PASS_NO
+
+/turf/CanPass(atom/movable/mover, turf/target)
+	if(!target) return FALSE
 
 	if(istype(mover)) // turf/Enter(...) will perform more advanced checks
 		return !density
 
-	else // Now, doing more detailed checks for air movement and air group formation
-		if(target.blocks_air||blocks_air)
-			return 0
-
-		for(var/obj/obstacle in src)
-			if(!obstacle.CanPass(mover, target, height, air_group))
-				return 0
-		if(target != src)
-			for(var/obj/obstacle in target)
-				if(!obstacle.CanPass(mover, src, height, air_group))
-					return 0
-
-		return 1
+/turf/CanZASPass(turf/T, is_zone)
+	if(T.blocks_air || src.blocks_air)
+		return FALSE
+	for(var/obj/obstacle in src)
+		if(!obstacle.CanZASPass(T, is_zone))
+			return FALSE
+	if(T != src)
+		for(var/obj/obstacle in T)
+			if(!obstacle.CanZASPass(src, is_zone))
+				return FALSE
+	return TRUE
 
 //Convenience function for atoms to update turfs they occupy
 /atom/movable/proc/update_nearby_tiles(need_rebuild)
@@ -50,8 +62,7 @@ atom/proc/c_airblock(turf/other)
 	#ifdef ZASDBG
 	ASSERT(isturf(other))
 	#endif
-	return (AIR_BLOCKED*!CanPass(null, other, 0, 0))|(ZONE_BLOCKED*!CanPass(null, other, 1.5, 1))
-
+	return (AIR_BLOCKED*!CanZASPass(other, FALSE))|(ZONE_BLOCKED*!CanZASPass(other, TRUE))
 
 turf/c_airblock(turf/other)
 	#ifdef ZASDBG

code/__defines/atmos.dm

@@ -92,4 +92,10 @@
 #define ATMOSTANK_OXYGEN        40000 // O2 is also important for airmix, but not as much as N2 as it's only 21% of it.
 #define ATMOSTANK_CO2           25000 // CO2 and PH are not critically important for station, only for toxins and alternative coolants, no need to store a lot of those.
 #define ATMOSTANK_PHORON        25000
-#define ATMOSTANK_NITROUSOXIDE  10000 // N2O doesn't have a real useful use, i guess it's on station just to allow refilling of sec's riot control canisters?
+#define ATMOSTANK_NITROUSOXIDE  10000 // N2O doesn't have a real useful use, i guess it's on station just to allow refilling of sec's riot control canisters?
+
+// Used for quickly making certain things allow airflow or not.
+// More complicated, conditional airflow should override CanZASPass().
+#define ATMOS_PASS_YES		1
+#define ATMOS_PASS_NO		0
+#define ATMOS_PASS_DENSITY	-1 // Just checks density.

code/game/gamemodes/meteor/meteors.dm

@@ -148,7 +148,7 @@
 		else
 			die(0)
 
-/obj/effect/meteor/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/effect/meteor/CanPass(atom/movable/mover, turf/target)
 	return istype(mover, /obj/effect/meteor) ? 1 : ..()
 
 /obj/effect/meteor/proc/ram_turf(var/turf/T)

code/game/machinery/OpTable.dm

@@ -48,13 +48,10 @@
 		qdel(src)
 	return
 
-/obj/machinery/optable/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0)) return 1
-
+/obj/machinery/optable/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
-	else
-		return 0
+		return TRUE
+	return FALSE
 
 /obj/machinery/optable/MouseDrop_T(obj/O as obj, mob/user as mob)
 

code/game/machinery/deployable.dm

@@ -128,13 +128,10 @@ for reference:
 				dismantle()
 			return
 
-/obj/structure/barricade/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)//So bullets will fly over and stuff.
-	if(air_group || (height==0))
-		return 1
+/obj/structure/barricade/CanPass(atom/movable/mover, turf/target)//So bullets will fly over and stuff.
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
-	else
-		return 0
+		return TRUE
+	return FALSE
 
 //Actual Deployable machinery stuff
 /obj/machinery/deployable
@@ -223,13 +220,10 @@ for reference:
 		anchored = !anchored
 		icon_state = "barrier[locked]"
 
-/obj/machinery/deployable/barrier/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)//So bullets will fly over and stuff.
-	if(air_group || (height==0))
-		return 1
+/obj/machinery/deployable/barrier/CanPass(atom/movable/mover, turf/target)//So bullets will fly over and stuff.
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
-	else
-		return 0
+		return TRUE
+	return FALSE
 
 /obj/machinery/deployable/barrier/proc/explode()
 

code/game/machinery/doors/airlock.dm

@@ -782,7 +782,7 @@ About the new airlock wires panel:
 			if (user)
 				src.attack_ai(user)
 
-/obj/machinery/door/airlock/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/machinery/door/airlock/CanPass(atom/movable/mover, turf/target)
 	if (src.isElectrified())
 		if (istype(mover, /obj/item))
 			var/obj/item/i = mover

code/game/machinery/doors/blast_door.dm

@@ -259,12 +259,14 @@
 	if(stat & BROKEN)
 		stat &= ~BROKEN
 
-
-/obj/machinery/door/blast/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group) return 1
+/*
+// This replicates the old functionality coded into CanPass() for this object, however it appeared to have made blast doors not airtight.
+// If for some reason this is actually needed for something important, uncomment this.
+/obj/machinery/door/blast/CanZASPass(turf/T, is_zone)
+	if(is_zone)
+		return ATMOS_PASS_YES
 	return ..()
-
-
+*/
 
 // SUBTYPE: Regular
 // Your classical blast door, found almost everywhere.

code/game/machinery/doors/door.dm

@@ -9,6 +9,7 @@
 	anchored = 1
 	opacity = 1
 	density = 1
+	can_atmos_pass = ATMOS_PASS_DENSITY
 	layer = DOOR_OPEN_LAYER
 	var/open_layer = DOOR_OPEN_LAYER
 	var/closed_layer = DOOR_CLOSED_LAYER
@@ -135,12 +136,15 @@
 			else
 				do_animate("deny")
 
-/obj/machinery/door/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group) return !block_air_zones
+/obj/machinery/door/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSGLASS))
 		return !opacity
 	return !density
 
+/obj/machinery/door/CanZASPass(turf/T, is_zone)
+	if(is_zone)
+		return block_air_zones ? ATMOS_PASS_NO : ATMOS_PASS_YES
+	return ..()
 
 /obj/machinery/door/proc/bumpopen(mob/user as mob)
 	if(operating)	return

code/game/machinery/doors/firedoor.dm

@@ -471,11 +471,10 @@
 	heat_proof = 1
 	air_properties_vary_with_direction = 1
 
-	CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+	CanPass(atom/movable/mover, turf/target)
 		if(istype(mover) && mover.checkpass(PASSGLASS))
 			return 1
 		if(get_dir(loc, target) == dir) //Make sure looking at appropriate border
-			if(air_group) return 0
 			return !density
 		else
 			return 1

code/game/machinery/doors/windowdoor.dm

@@ -84,14 +84,27 @@
 		open()
 		addtimer(CALLBACK(src, .proc/close), check_access(null)? 50 : 20)
 
-/obj/machinery/door/window/CanPass(atom/movable/mover, turf/target, height, air_group)
+<<<<<<< HEAD
+/obj/machinery/door/window/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
 	if(istype(mover) && mover.checkpass(PASSGLASS))
 		return 1
 	if(get_dir(mover, loc) == turn(dir, 180)) //Make sure looking at appropriate border
 		if(air_group) return 0
+=======
+/obj/machinery/door/window/CanPass(atom/movable/mover, turf/target)
+	if(istype(mover) && mover.checkpass(PASSGLASS))
+		return TRUE
+	if(get_dir(mover, loc) == turn(dir, 180)) //Make sure looking at appropriate border
+>>>>>>> 4122c65... Merge pull request #5947 from Neerti/bump_fixes
 		return !density
-	else
-		return 1
+	return TRUE
+
+/obj/machinery/door/window/CanZASPass(turf/T, is_zone)
+	if(get_dir(T, loc) == turn(dir, 180))
+		if(is_zone) // No merging allowed.
+			return ATMOS_PASS_NO
+		return ..() // Air can flow if open (density == FALSE).
+	return ATMOS_PASS_YES // Windoors don't block if not facing the right way.
 
 /obj/machinery/door/window/CheckExit(atom/movable/mover as mob|obj, turf/target as turf)
 	if(istype(mover) && mover.checkpass(PASSGLASS))

code/game/machinery/iv_drip.dm

@@ -180,7 +180,7 @@
 
 	to_chat(user, "<span class='notice'>[attached ? attached : "No one"] is attached.</span>")
 
-/obj/machinery/iv_drip/CanPass(atom/movable/mover, turf/target, height = 0, air_group = 0)
-	if(height && istype(mover) && mover.checkpass(PASSTABLE)) //allow bullets, beams, thrown objects, mice, drones, and the like through.
-		return 1
+/obj/machinery/iv_drip/CanPass(atom/movable/mover, turf/target)
+	if(istype(mover) && mover.checkpass(PASSTABLE)) //allow bullets, beams, thrown objects, mice, drones, and the like through.
+		return TRUE
 	return ..()

code/game/mecha/mech_sensor.dm

@@ -15,14 +15,14 @@
 	var/frequency = 1379
 	var/datum/radio_frequency/radio_connection
 
-/obj/machinery/mech_sensor/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(!src.enabled()) return 1
-	if(air_group || (height==0)) return 1
+/obj/machinery/mech_sensor/CanPass(atom/movable/mover, turf/target)
+	if(!enabled())
+		return TRUE
 
-	if ((get_dir(loc, target) & dir) && src.is_blocked(mover))
+	if((get_dir(loc, target) & dir) && src.is_blocked(mover))
 		src.give_feedback(mover)
-		return 0
-	return 1
+		return FALSE
+	return TRUE
 
 /obj/machinery/mech_sensor/proc/is_blocked(O as obj)
 	if(istype(O, /obj/mecha/medical/odysseus))

code/game/objects/effects/alien/aliens.dm

@@ -26,6 +26,7 @@
 	density = 1
 	opacity = 1
 	anchored = 1
+	can_atmos_pass = ATMOS_PASS_NO
 	var/health = 200
 	//var/mob/living/affecting = null
 
@@ -128,8 +129,7 @@
 	..()
 	return
 
-/obj/effect/alien/resin/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group) return 0
+/obj/effect/alien/resin/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSGLASS))
 		return !opacity
 	return !density

code/game/objects/effects/chem/foam.dm

@@ -130,6 +130,7 @@
 	anchored = 1
 	name = "foamed metal"
 	desc = "A lightweight foamed metal wall."
+	can_atmos_pass = ATMOS_PASS_NO
 	var/metal = 1 // 1 = aluminum, 2 = iron
 
 /obj/structure/foamedmetal/New()
@@ -178,8 +179,3 @@
 		qdel(src)
 	else
 		user << "<span class='notice'>You hit the metal foam to no effect.</span>"
-
-/obj/structure/foamedmetal/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
-	if(air_group)
-		return 0
-	return !density

code/game/objects/effects/spiders.dm

@@ -62,17 +62,23 @@
 		icon_state = "stickyweb2"
 	return ..()
 
+<<<<<<< HEAD
 /obj/effect/spider/stickyweb/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
 	if(air_group || (height==0)) return 1
 	if(istype(mover, /mob/living/simple_mob/animal/giant_spider))
 		return 1
+=======
+/obj/effect/spider/stickyweb/CanPass(atom/movable/mover, turf/target)
+	if(istype(mover, /mob/living/simple_mob/animal/giant_spider))
+		return TRUE
+>>>>>>> 4122c65... Merge pull request #5947 from Neerti/bump_fixes
 	else if(istype(mover, /mob/living))
 		if(prob(50))
-			mover << "<span class='warning'>You get stuck in \the [src] for a moment.</span>"
-			return 0
+			to_chat(mover, span("warning", "You get stuck in \the [src] for a moment."))
+			return FALSE
 	else if(istype(mover, /obj/item/projectile))
 		return prob(30)
-	return 1
+	return TRUE
 
 /obj/effect/spider/eggcluster
 	name = "egg cluster"

code/game/objects/effects/zone_divider.dm

@@ -8,13 +8,12 @@
 	density = 0
 	opacity = 0
 
-/obj/effect/zone_divider/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/effect/zone_divider/CanZASPass(turf/T, is_zone)
  	// Special case to prevent us from being part of a zone during the first air master tick.
  	// We must merge ourselves into a zone on next tick.  This will cause a bit of lag on
  	// startup, but it can't really be helped you know?
 	if(air_master && air_master.current_cycle == 0)
 		spawn(1)
 			air_master.mark_for_update(get_turf(src))
-		return 0
-	return !air_group // Anything except zones can pass
-
+		return ATMOS_PASS_NO
+	return is_zone ? ATMOS_PASS_NO : ATMOS_PASS_YES // Anything except zones can pass

code/game/objects/items/weapons/policetape.dm

@@ -286,16 +286,23 @@ var/list/tape_roll_applications = list()
 		update_icon()
 		name = "crumpled [name]"
 
-/obj/item/tape/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/item/tape/CanPass(atom/movable/mover, turf/target)
 	if(!lifted && ismob(mover))
 		var/mob/M = mover
 		add_fingerprint(M)
+<<<<<<< HEAD
 		if (!allowed(M))	//only select few learn art of not crumpling the tape
 			M << "<span class='warning'>You are not supposed to go past [src]...</span>"
 			if(M.a_intent == I_HELP && !(istype(M, /mob/living/simple_mob)))
 				return 0
+=======
+		if(!allowed(M))	//only select few learn art of not crumpling the tape
+			to_chat(M, span("warning", "You are not supposed to go past \the [src]..."))
+			if(M.a_intent == I_HELP && !(istype(M, /mob/living/simple_mob)))
+				return FALSE
+>>>>>>> 4122c65... Merge pull request #5947 from Neerti/bump_fixes
 			crumple()
-	return ..(mover)
+	return ..()
 
 /obj/item/tape/attackby(obj/item/weapon/W as obj, mob/user as mob)
 	breaktape(user)

code/game/objects/structures/cliff.dm

@@ -1,239 +1,236 @@
-GLOBAL_LIST_EMPTY(cliff_icon_cache)
-
-/*
-Cliffs give a visual illusion of depth by seperating two places while presenting a 'top' and 'bottom' side.
-
-Mobs moving into a cliff from the bottom side will simply bump into it and be denied moving into the tile,
-where as mobs moving into a cliff from the top side will 'fall' off the cliff, forcing them to the bottom, causing significant damage and stunning them.
-
-Mobs can climb this while wearing climbing equipment by clickdragging themselves onto a cliff, as if it were a table.
-
-Flying mobs can pass over all cliffs with no risk of falling.
-
-Projectiles and thrown objects can pass, however if moving upwards, there is a chance for it to be stopped by the cliff.
-This makes fighting something that is on top of a cliff more challenging.
-
-As a note, dir points upwards, e.g. pointing WEST means the left side is 'up', and the right side is 'down'.
-
-When mapping these in, be sure to give at least a one tile clearance, as NORTH facing cliffs expand to
-two tiles on initialization, and which way a cliff is facing may change during maploading.
-*/
-
-/obj/structure/cliff
-	name = "cliff"
-	desc = "A steep rock ledge. You might be able to climb it if you feel bold enough."
-	description_info = "Walking off the edge of a cliff while on top will cause you to fall off, causing severe injury.<br>\
-	You can climb this cliff if wearing special climbing equipment, by click-dragging yourself onto the cliff.<br>\
-	Projectiles traveling up a cliff may hit the cliff instead, making it more difficult to fight something \
-	on top."
-	icon = 'icons/obj/flora/rocks.dmi'
-
-	anchored = TRUE
-	density = TRUE
-	opacity = FALSE
-	climbable = TRUE
-	climb_delay = 10 SECONDS
-	block_turf_edges = TRUE // Don't want turf edges popping up from the cliff edge.
-	register_as_dangerous_object = TRUE
-
-	var/icon_variant = null // Used to make cliffs less repeative by having a selection of sprites to display.
-	var/corner = FALSE // Used for icon things.
-	var/ramp = FALSE // Ditto.
-	var/bottom = FALSE // Used for 'bottom' typed cliffs, to avoid infinite cliffs, and for icons.
-
-	var/is_double_cliff = FALSE // Set to true when making the two-tile cliffs, used for projectile checks.
-	var/uphill_penalty = 30 // Odds of a projectile not making it up the cliff.
-
-// These arrange their sprites at runtime, as opposed to being statically placed in the map file.
-/obj/structure/cliff/automatic
-	icon_state = "cliffbuilder"
-	dir = NORTH
-
-/obj/structure/cliff/automatic/corner
-	icon_state = "cliffbuilder-corner"
-	dir = NORTHEAST
-	corner = TRUE
-
-// Tiny part that doesn't block, used for making 'ramps'.
-/obj/structure/cliff/automatic/ramp
-	icon_state = "cliffbuilder-ramp"
-	dir = NORTHEAST
-	density = FALSE
-	ramp = TRUE
-
-// Made automatically as needed by automatic cliffs.
-/obj/structure/cliff/bottom
-	bottom = TRUE
-
-/obj/structure/cliff/automatic/Initialize()
-	..()
-	return INITIALIZE_HINT_LATELOAD
-
-// Paranoid about the maploader, direction is very important to cliffs, since they may get bigger if initialized while facing NORTH.
-/obj/structure/cliff/automatic/LateInitialize()
-	if(dir in GLOB.cardinal)
-		icon_variant = pick("a", "b", "c")
-
-	if(dir & NORTH && !bottom) // North-facing cliffs require more cliffs to be made.
-		make_bottom()
-
-	update_icon()
-
-/obj/structure/cliff/proc/make_bottom()
-	// First, make sure there's room to put the bottom side.
-	var/turf/T = locate(x, y - 1, z)
-	if(!istype(T))
-		return FALSE
-
-	// Now make the bottom cliff have mostly the same variables.
-	var/obj/structure/cliff/bottom/bottom = new(T)
-	is_double_cliff = TRUE
-	climb_delay /= 2 // Since there are two cliffs to climb when going north, both take half the time.
-
-	bottom.dir = dir
-	bottom.is_double_cliff = TRUE
-	bottom.climb_delay = climb_delay
-	bottom.icon_variant = icon_variant
-	bottom.corner = corner
-	bottom.ramp = ramp
-	bottom.layer = layer - 0.1
-	bottom.density = density
-	bottom.update_icon()
-
-/obj/structure/cliff/set_dir(new_dir)
-	..()
-	update_icon()
-
-/obj/structure/cliff/update_icon()
-	icon_state = "cliff-[dir][icon_variant][bottom ? "-bottom" : ""][corner ? "-corner" : ""][ramp ? "-ramp" : ""]"
-
-	// Now for making the top-side look like a different turf.
-	var/turf/T = get_step(src, dir)
-	if(!istype(T))
-		return
-
-	var/subtraction_icon_state = "[icon_state]-subtract"
-	var/cache_string = "[icon_state]_[T.icon]_[T.icon_state]"
-	if(T && subtraction_icon_state in icon_states(icon))
-		cut_overlays()
-		// If we've made the same icon before, just recycle it.
-		if(cache_string in GLOB.cliff_icon_cache)
-			add_overlay(GLOB.cliff_icon_cache[cache_string])
-
-		else // Otherwise make a new one, but only once.
-			var/icon/underlying_ground = icon(T.icon, T.icon_state, T.dir)
-			var/icon/subtract = icon(icon, subtraction_icon_state)
-			underlying_ground.Blend(subtract, ICON_SUBTRACT)
-			var/image/final = image(underlying_ground)
-			final.layer = src.layer - 0.2
-			GLOB.cliff_icon_cache[cache_string] = final
-			add_overlay(final)
-
-
-// Movement-related code.
-
-/obj/structure/cliff/CanPass(atom/movable/mover, turf/target, height = 0, air_group = 0)
-	if(air_group || height == 0)
-		return TRUE // Airflow can always pass.
-
-	else if(isliving(mover))
-		var/mob/living/L = mover
-		if(L.hovering) // Flying mobs can always pass.
-			return TRUE
-		return ..()
-
-	// Projectiles and objects flying 'upward' have a chance to hit the cliff instead, wasting the shot.
-	else if(istype(mover, /obj))
-		var/obj/O = mover
-		if(check_shield_arc(src, dir, O)) // This is actually for mobs but it will work for our purposes as well.
-			if(prob(uphill_penalty / (1 + is_double_cliff) )) // Firing upwards facing NORTH means it will likely have to pass through two cliffs, so the chance is halved.
-				return FALSE
-		return TRUE
-
-/obj/structure/cliff/Bumped(atom/A)
-	if(isliving(A))
-		var/mob/living/L = A
-		if(should_fall(L))
-			fall_off_cliff(L)
-			return
-	..()
-
-/obj/structure/cliff/proc/should_fall(mob/living/L)
-	if(L.hovering)
-		return FALSE
-
-	var/turf/T = get_turf(L)
-	if(T && get_dir(T, loc) & reverse_dir[dir]) // dir points 'up' the cliff, e.g. cliff pointing NORTH will cause someone to fall if moving SOUTH into it.
-		return TRUE
-	return FALSE
-
-/obj/structure/cliff/proc/fall_off_cliff(mob/living/L)
-	if(!istype(L))
-		return FALSE
-	var/turf/T = get_step(src, reverse_dir[dir])
-	var/displaced = FALSE
-
-	if(dir in list(EAST, WEST)) // Apply an offset if flying sideways, to help maintain the illusion of depth.
-		for(var/i = 1 to 2)
-			var/turf/new_T = locate(T.x, T.y - i, T.z)
-			if(!new_T || locate(/obj/structure/cliff) in new_T)
-				break
-			T = new_T
-			displaced = TRUE
-
-	if(istype(T))
-		visible_message(span("danger", "\The [L] falls off \the [src]!"))
-		L.forceMove(T)
-
-		// Do the actual hurting. Double cliffs do halved damage due to them most likely hitting twice.
-		var/harm = !is_double_cliff ? 1 : 0.5
-		if(istype(L.buckled, /obj/vehicle)) // People falling off in vehicles will take less damage, but will damage the vehicle severely.
-			var/obj/vehicle/vehicle = L.buckled
-			vehicle.adjust_health(40 * harm)
-			to_chat(L, span("warning", "\The [vehicle] absorbs some of the impact, damaging it."))
-			harm /= 2
-
-		playsound(L, 'sound/effects/break_stone.ogg', 70, 1)
-		L.Weaken(5 * harm)
-		var/fall_time = 3
-		if(displaced) // Make the fall look more natural when falling sideways.
-			L.pixel_z = 32 * 2
-			animate(L, pixel_z = 0, time = fall_time)
-		sleep(fall_time) // A brief delay inbetween the two sounds helps sell the 'ouch' effect.
-		playsound(L, "punch", 70, 1)
-		shake_camera(L, 1, 1)
-		visible_message(span("danger", "\The [L] hits the ground!"))
-
-		// The bigger they are, the harder they fall.
-		// They will take at least 20 damage at the minimum, and tries to scale up to 40% of their max health.
-		// This scaling is capped at 100 total damage, which occurs if the thing that fell has more than 250 health.
-		var/damage = between(20, L.getMaxHealth() * 0.4, 100)
-		var/target_zone = ran_zone()
-		var/blocked = L.run_armor_check(target_zone, "melee") * harm
-		var/soaked = L.get_armor_soak(target_zone, "melee") * harm
-
-		L.apply_damage(damage * harm, BRUTE, target_zone, blocked, soaked, used_weapon=src)
-
-		// Now fall off more cliffs below this one if they exist.
-		var/obj/structure/cliff/bottom_cliff = locate() in T
-		if(bottom_cliff)
-			visible_message(span("danger", "\The [L] rolls down towards \the [bottom_cliff]!"))
-			sleep(5)
-			bottom_cliff.fall_off_cliff(L)
-
-/obj/structure/cliff/can_climb(mob/living/user, post_climb_check = FALSE)
-	// Cliff climbing requires climbing gear.
-	if(ishuman(user))
-		var/mob/living/carbon/human/H = user
-		var/obj/item/clothing/shoes/shoes = H.shoes
-		if(shoes && shoes.rock_climbing)
-			return ..() // Do the other checks too.
-
-	to_chat(user, span("warning", "\The [src] is too steep to climb unassisted."))
-	return FALSE
-
-// This tells AI mobs to not be dumb and step off cliffs willingly.
-/obj/structure/cliff/is_safe_to_step(mob/living/L)
-	if(should_fall(L))
-		return FALSE
-	return ..()
+GLOBAL_LIST_EMPTY(cliff_icon_cache)
+
+/*
+Cliffs give a visual illusion of depth by seperating two places while presenting a 'top' and 'bottom' side.
+
+Mobs moving into a cliff from the bottom side will simply bump into it and be denied moving into the tile,
+where as mobs moving into a cliff from the top side will 'fall' off the cliff, forcing them to the bottom, causing significant damage and stunning them.
+
+Mobs can climb this while wearing climbing equipment by clickdragging themselves onto a cliff, as if it were a table.
+
+Flying mobs can pass over all cliffs with no risk of falling.
+
+Projectiles and thrown objects can pass, however if moving upwards, there is a chance for it to be stopped by the cliff.
+This makes fighting something that is on top of a cliff more challenging.
+
+As a note, dir points upwards, e.g. pointing WEST means the left side is 'up', and the right side is 'down'.
+
+When mapping these in, be sure to give at least a one tile clearance, as NORTH facing cliffs expand to
+two tiles on initialization, and which way a cliff is facing may change during maploading.
+*/
+
+/obj/structure/cliff
+	name = "cliff"
+	desc = "A steep rock ledge. You might be able to climb it if you feel bold enough."
+	description_info = "Walking off the edge of a cliff while on top will cause you to fall off, causing severe injury.<br>\
+	You can climb this cliff if wearing special climbing equipment, by click-dragging yourself onto the cliff.<br>\
+	Projectiles traveling up a cliff may hit the cliff instead, making it more difficult to fight something \
+	on top."
+	icon = 'icons/obj/flora/rocks.dmi'
+
+	anchored = TRUE
+	density = TRUE
+	opacity = FALSE
+	climbable = TRUE
+	climb_delay = 10 SECONDS
+	block_turf_edges = TRUE // Don't want turf edges popping up from the cliff edge.
+	register_as_dangerous_object = TRUE
+
+	var/icon_variant = null // Used to make cliffs less repeative by having a selection of sprites to display.
+	var/corner = FALSE // Used for icon things.
+	var/ramp = FALSE // Ditto.
+	var/bottom = FALSE // Used for 'bottom' typed cliffs, to avoid infinite cliffs, and for icons.
+
+	var/is_double_cliff = FALSE // Set to true when making the two-tile cliffs, used for projectile checks.
+	var/uphill_penalty = 30 // Odds of a projectile not making it up the cliff.
+
+// These arrange their sprites at runtime, as opposed to being statically placed in the map file.
+/obj/structure/cliff/automatic
+	icon_state = "cliffbuilder"
+	dir = NORTH
+
+/obj/structure/cliff/automatic/corner
+	icon_state = "cliffbuilder-corner"
+	dir = NORTHEAST
+	corner = TRUE
+
+// Tiny part that doesn't block, used for making 'ramps'.
+/obj/structure/cliff/automatic/ramp
+	icon_state = "cliffbuilder-ramp"
+	dir = NORTHEAST
+	density = FALSE
+	ramp = TRUE
+
+// Made automatically as needed by automatic cliffs.
+/obj/structure/cliff/bottom
+	bottom = TRUE
+
+/obj/structure/cliff/automatic/Initialize()
+	..()
+	return INITIALIZE_HINT_LATELOAD
+
+// Paranoid about the maploader, direction is very important to cliffs, since they may get bigger if initialized while facing NORTH.
+/obj/structure/cliff/automatic/LateInitialize()
+	if(dir in GLOB.cardinal)
+		icon_variant = pick("a", "b", "c")
+
+	if(dir & NORTH && !bottom) // North-facing cliffs require more cliffs to be made.
+		make_bottom()
+
+	update_icon()
+
+/obj/structure/cliff/proc/make_bottom()
+	// First, make sure there's room to put the bottom side.
+	var/turf/T = locate(x, y - 1, z)
+	if(!istype(T))
+		return FALSE
+
+	// Now make the bottom cliff have mostly the same variables.
+	var/obj/structure/cliff/bottom/bottom = new(T)
+	is_double_cliff = TRUE
+	climb_delay /= 2 // Since there are two cliffs to climb when going north, both take half the time.
+
+	bottom.dir = dir
+	bottom.is_double_cliff = TRUE
+	bottom.climb_delay = climb_delay
+	bottom.icon_variant = icon_variant
+	bottom.corner = corner
+	bottom.ramp = ramp
+	bottom.layer = layer - 0.1
+	bottom.density = density
+	bottom.update_icon()
+
+/obj/structure/cliff/set_dir(new_dir)
+	..()
+	update_icon()
+
+/obj/structure/cliff/update_icon()
+	icon_state = "cliff-[dir][icon_variant][bottom ? "-bottom" : ""][corner ? "-corner" : ""][ramp ? "-ramp" : ""]"
+
+	// Now for making the top-side look like a different turf.
+	var/turf/T = get_step(src, dir)
+	if(!istype(T))
+		return
+
+	var/subtraction_icon_state = "[icon_state]-subtract"
+	var/cache_string = "[icon_state]_[T.icon]_[T.icon_state]"
+	if(T && subtraction_icon_state in icon_states(icon))
+		cut_overlays()
+		// If we've made the same icon before, just recycle it.
+		if(cache_string in GLOB.cliff_icon_cache)
+			add_overlay(GLOB.cliff_icon_cache[cache_string])
+
+		else // Otherwise make a new one, but only once.
+			var/icon/underlying_ground = icon(T.icon, T.icon_state, T.dir)
+			var/icon/subtract = icon(icon, subtraction_icon_state)
+			underlying_ground.Blend(subtract, ICON_SUBTRACT)
+			var/image/final = image(underlying_ground)
+			final.layer = src.layer - 0.2
+			GLOB.cliff_icon_cache[cache_string] = final
+			add_overlay(final)
+
+
+// Movement-related code.
+
+/obj/structure/cliff/CanPass(atom/movable/mover, turf/target)
+	if(isliving(mover))
+		var/mob/living/L = mover
+		if(L.hovering) // Flying mobs can always pass.
+			return TRUE
+		return ..()
+
+	// Projectiles and objects flying 'upward' have a chance to hit the cliff instead, wasting the shot.
+	else if(istype(mover, /obj))
+		var/obj/O = mover
+		if(check_shield_arc(src, dir, O)) // This is actually for mobs but it will work for our purposes as well.
+			if(prob(uphill_penalty / (1 + is_double_cliff) )) // Firing upwards facing NORTH means it will likely have to pass through two cliffs, so the chance is halved.
+				return FALSE
+		return TRUE
+
+/obj/structure/cliff/Bumped(atom/A)
+	if(isliving(A))
+		var/mob/living/L = A
+		if(should_fall(L))
+			fall_off_cliff(L)
+			return
+	..()
+
+/obj/structure/cliff/proc/should_fall(mob/living/L)
+	if(L.hovering)
+		return FALSE
+
+	var/turf/T = get_turf(L)
+	if(T && get_dir(T, loc) & reverse_dir[dir]) // dir points 'up' the cliff, e.g. cliff pointing NORTH will cause someone to fall if moving SOUTH into it.
+		return TRUE
+	return FALSE
+
+/obj/structure/cliff/proc/fall_off_cliff(mob/living/L)
+	if(!istype(L))
+		return FALSE
+	var/turf/T = get_step(src, reverse_dir[dir])
+	var/displaced = FALSE
+
+	if(dir in list(EAST, WEST)) // Apply an offset if flying sideways, to help maintain the illusion of depth.
+		for(var/i = 1 to 2)
+			var/turf/new_T = locate(T.x, T.y - i, T.z)
+			if(!new_T || locate(/obj/structure/cliff) in new_T)
+				break
+			T = new_T
+			displaced = TRUE
+
+	if(istype(T))
+		visible_message(span("danger", "\The [L] falls off \the [src]!"))
+		L.forceMove(T)
+
+		// Do the actual hurting. Double cliffs do halved damage due to them most likely hitting twice.
+		var/harm = !is_double_cliff ? 1 : 0.5
+		if(istype(L.buckled, /obj/vehicle)) // People falling off in vehicles will take less damage, but will damage the vehicle severely.
+			var/obj/vehicle/vehicle = L.buckled
+			vehicle.adjust_health(40 * harm)
+			to_chat(L, span("warning", "\The [vehicle] absorbs some of the impact, damaging it."))
+			harm /= 2
+
+		playsound(L, 'sound/effects/break_stone.ogg', 70, 1)
+		L.Weaken(5 * harm)
+		var/fall_time = 3
+		if(displaced) // Make the fall look more natural when falling sideways.
+			L.pixel_z = 32 * 2
+			animate(L, pixel_z = 0, time = fall_time)
+		sleep(fall_time) // A brief delay inbetween the two sounds helps sell the 'ouch' effect.
+		playsound(L, "punch", 70, 1)
+		shake_camera(L, 1, 1)
+		visible_message(span("danger", "\The [L] hits the ground!"))
+
+		// The bigger they are, the harder they fall.
+		// They will take at least 20 damage at the minimum, and tries to scale up to 40% of their max health.
+		// This scaling is capped at 100 total damage, which occurs if the thing that fell has more than 250 health.
+		var/damage = between(20, L.getMaxHealth() * 0.4, 100)
+		var/target_zone = ran_zone()
+		var/blocked = L.run_armor_check(target_zone, "melee") * harm
+		var/soaked = L.get_armor_soak(target_zone, "melee") * harm
+
+		L.apply_damage(damage * harm, BRUTE, target_zone, blocked, soaked, used_weapon=src)
+
+		// Now fall off more cliffs below this one if they exist.
+		var/obj/structure/cliff/bottom_cliff = locate() in T
+		if(bottom_cliff)
+			visible_message(span("danger", "\The [L] rolls down towards \the [bottom_cliff]!"))
+			sleep(5)
+			bottom_cliff.fall_off_cliff(L)
+
+/obj/structure/cliff/can_climb(mob/living/user, post_climb_check = FALSE)
+	// Cliff climbing requires climbing gear.
+	if(ishuman(user))
+		var/mob/living/carbon/human/H = user
+		var/obj/item/clothing/shoes/shoes = H.shoes
+		if(shoes && shoes.rock_climbing)
+			return ..() // Do the other checks too.
+
+	to_chat(user, span("warning", "\The [src] is too steep to climb unassisted."))
+	return FALSE
+
+// This tells AI mobs to not be dumb and step off cliffs willingly.
+/obj/structure/cliff/is_safe_to_step(mob/living/L)
+	if(should_fall(L))
+		return FALSE
+	return ..()

code/game/objects/structures/coathanger.dm

@@ -27,7 +27,7 @@
 		user << "<span class='notice'>You cannot hang [W] on [src]</span>"
 		return ..()
 
-/obj/structure/coatrack/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/structure/coatrack/CanPass(atom/movable/mover, turf/target)
 	var/can_hang = 0
 	for (var/T in allowed)
 		if(istype(mover,T))

code/game/objects/structures/crates_lockers/closets.dm

@@ -69,7 +69,7 @@
 		else
 			to_chat(user, "It is full.")
 
-/obj/structure/closet/CanPass(atom/movable/mover, turf/target, height, air_group)
+/obj/structure/closet/CanPass(atom/movable/mover, turf/target)
 	if(wall_mounted)
 		return TRUE
 	return ..()

code/game/objects/structures/crates_lockers/closets/coffin.dm

@@ -39,7 +39,7 @@
 							"<span class='notice'>You stop climbing into \the [src.name].</span>")
 	return
 
-/obj/structure/closet/grave/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/structure/closet/grave/CanPass(atom/movable/mover, turf/target)
 	if(opened && ismob(mover))
 		var/mob/M = mover
 		add_fingerprint(M)

code/game/objects/structures/fence.dm

@@ -1,179 +1,179 @@
-//Chain link fences
-//Sprites ported from /VG/
-
-#define CUT_TIME 10 SECONDS
-#define CLIMB_TIME 5 SECONDS
-
-#define NO_HOLE 0 //section is intact
-#define MEDIUM_HOLE 1 //medium hole in the section - can climb through
-#define LARGE_HOLE 2 //large hole in the section - can walk through
-#define MAX_HOLE_SIZE LARGE_HOLE
-
-/obj/structure/fence
-	name = "fence"
-	desc = "A chain link fence. Not as effective as a wall, but generally it keeps people out."
-	description_info = "Projectiles can freely pass fences."
-	density = TRUE
-	anchored = TRUE
-
-	icon = 'icons/obj/fence.dmi'
-	icon_state = "straight"
-
-	var/cuttable = TRUE
-	var/hole_size= NO_HOLE
-	var/invulnerable = FALSE
-
-/obj/structure/fence/Initialize()
-	update_cut_status()
-	return ..()
-
-/obj/structure/fence/examine(mob/user)
-	. = ..()
-
-	switch(hole_size)
-		if(MEDIUM_HOLE)
-			user.show_message("There is a large hole in \the [src].")
-		if(LARGE_HOLE)
-			user.show_message("\The [src] has been completely cut through.")
-
-/obj/structure/fence/get_description_interaction()
-	var/list/results = list()
-	if(cuttable && !invulnerable && hole_size < MAX_HOLE_SIZE)
-		results += "[desc_panel_image("wirecutters")]to [hole_size > NO_HOLE ? "expand the":"cut a"] hole into the fence, allowing passage."
-	return results
-
-/obj/structure/fence/end
-	icon_state = "end"
-	cuttable = FALSE
-
-/obj/structure/fence/corner
-	icon_state = "corner"
-	cuttable = FALSE
-
-/obj/structure/fence/post
-	icon_state = "post"
-	cuttable = FALSE
-
-/obj/structure/fence/cut/medium
-	icon_state = "straight_cut2"
-	hole_size = MEDIUM_HOLE
-
-/obj/structure/fence/cut/large
-	icon_state = "straight_cut3"
-	hole_size = LARGE_HOLE
-
-// Projectiles can pass through fences.
-/obj/structure/fence/CanPass(atom/movable/mover, turf/target, height = 0, air_group = 0)
-	if(istype(mover, /obj/item/projectile))
-		return TRUE
-	return ..()
-
-/obj/structure/fence/attackby(obj/item/W, mob/user)
-	if(W.is_wirecutter())
-		if(!cuttable)
-			to_chat(user, span("warning", "This section of the fence can't be cut."))
-			return
-		if(invulnerable)
-			to_chat(user, span("warning", "This fence is too strong to cut through."))
-			return
-		var/current_stage = hole_size
-		if(current_stage >= MAX_HOLE_SIZE)
-			to_chat(user, span("notice", "This fence has too much cut out of it already."))
-			return
-
-		user.visible_message(span("danger", "\The [user] starts cutting through \the [src] with \the [W]."),\
-		span("danger", "You start cutting through \the [src] with \the [W]."))
-		playsound(src, W.usesound, 50, 1)
-
-		if(do_after(user, CUT_TIME * W.toolspeed, target = src))
-			if(current_stage == hole_size)
-				switch(++hole_size)
-					if(MEDIUM_HOLE)
-						visible_message(span("notice", "\The [user] cuts into \the [src] some more."))
-						to_chat(user, span("notice", "You could probably fit yourself through that hole now. Although climbing through would be much faster if you made it even bigger."))
-						climbable = TRUE
-					if(LARGE_HOLE)
-						visible_message(span("notice", "\The [user] completely cuts through \the [src]."))
-						to_chat(user, span("notice", "The hole in \the [src] is now big enough to walk through."))
-						climbable = FALSE
-				update_cut_status()
-	return TRUE
-
-/obj/structure/fence/proc/update_cut_status()
-	if(!cuttable)
-		return
-	density = TRUE
-
-	switch(hole_size)
-		if(NO_HOLE)
-			icon_state = initial(icon_state)
-		if(MEDIUM_HOLE)
-			icon_state = "straight_cut2"
-		if(LARGE_HOLE)
-			icon_state = "straight_cut3"
-			density = FALSE
-
-//FENCE DOORS
-
-/obj/structure/fence/door
-	name = "fence door"
-	desc = "Not very useful without a real lock."
-	icon_state = "door_closed"
-	cuttable = FALSE
-	var/open = FALSE
-	var/locked = FALSE
-
-/obj/structure/fence/door/Initialize()
-	update_door_status()
-	return ..()
-
-/obj/structure/fence/door/opened
-	icon_state = "door_opened"
-	open = TRUE
-	density = TRUE
-
-/obj/structure/fence/door/locked
-	desc = "It looks like it has a strong padlock attached."
-	locked = TRUE
-
-/obj/structure/fence/door/attack_hand(mob/user)
-	if(can_open(user))
-		toggle(user)
-	else
-		to_chat(user, span("warning", "\The [src] is [!open ? "locked" : "stuck open"]."))
-
-	return TRUE
-
-/obj/structure/fence/door/proc/toggle(mob/user)
-	switch(open)
-		if(FALSE)
-			visible_message(span("notice", "\The [user] opens \the [src]."))
-			open = TRUE
-		if(TRUE)
-			visible_message(span("notice", "\The [user] closes \the [src]."))
-			open = FALSE
-
-	update_door_status()
-	playsound(src, 'sound/machines/click.ogg', 100, 1)
-
-/obj/structure/fence/door/proc/update_door_status()
-	switch(open)
-		if(FALSE)
-			density = TRUE
-			icon_state = "door_closed"
-		if(TRUE)
-			density = FALSE
-			icon_state = "door_opened"
-
-/obj/structure/fence/door/proc/can_open(mob/user)
-	if(locked)
-		return FALSE
-	return TRUE
-
-#undef CUT_TIME
-#undef CLIMB_TIME
-
-#undef NO_HOLE
-#undef MEDIUM_HOLE
-#undef LARGE_HOLE
+//Chain link fences
+//Sprites ported from /VG/
+
+#define CUT_TIME 10 SECONDS
+#define CLIMB_TIME 5 SECONDS
+
+#define NO_HOLE 0 //section is intact
+#define MEDIUM_HOLE 1 //medium hole in the section - can climb through
+#define LARGE_HOLE 2 //large hole in the section - can walk through
+#define MAX_HOLE_SIZE LARGE_HOLE
+
+/obj/structure/fence
+	name = "fence"
+	desc = "A chain link fence. Not as effective as a wall, but generally it keeps people out."
+	description_info = "Projectiles can freely pass fences."
+	density = TRUE
+	anchored = TRUE
+
+	icon = 'icons/obj/fence.dmi'
+	icon_state = "straight"
+
+	var/cuttable = TRUE
+	var/hole_size= NO_HOLE
+	var/invulnerable = FALSE
+
+/obj/structure/fence/Initialize()
+	update_cut_status()
+	return ..()
+
+/obj/structure/fence/examine(mob/user)
+	. = ..()
+
+	switch(hole_size)
+		if(MEDIUM_HOLE)
+			user.show_message("There is a large hole in \the [src].")
+		if(LARGE_HOLE)
+			user.show_message("\The [src] has been completely cut through.")
+
+/obj/structure/fence/get_description_interaction()
+	var/list/results = list()
+	if(cuttable && !invulnerable && hole_size < MAX_HOLE_SIZE)
+		results += "[desc_panel_image("wirecutters")]to [hole_size > NO_HOLE ? "expand the":"cut a"] hole into the fence, allowing passage."
+	return results
+
+/obj/structure/fence/end
+	icon_state = "end"
+	cuttable = FALSE
+
+/obj/structure/fence/corner
+	icon_state = "corner"
+	cuttable = FALSE
+
+/obj/structure/fence/post
+	icon_state = "post"
+	cuttable = FALSE
+
+/obj/structure/fence/cut/medium
+	icon_state = "straight_cut2"
+	hole_size = MEDIUM_HOLE
+
+/obj/structure/fence/cut/large
+	icon_state = "straight_cut3"
+	hole_size = LARGE_HOLE
+
+// Projectiles can pass through fences.
+/obj/structure/fence/CanPass(atom/movable/mover, turf/target)
+	if(istype(mover, /obj/item/projectile))
+		return TRUE
+	return ..()
+
+/obj/structure/fence/attackby(obj/item/W, mob/user)
+	if(W.is_wirecutter())
+		if(!cuttable)
+			to_chat(user, span("warning", "This section of the fence can't be cut."))
+			return
+		if(invulnerable)
+			to_chat(user, span("warning", "This fence is too strong to cut through."))
+			return
+		var/current_stage = hole_size
+		if(current_stage >= MAX_HOLE_SIZE)
+			to_chat(user, span("notice", "This fence has too much cut out of it already."))
+			return
+
+		user.visible_message(span("danger", "\The [user] starts cutting through \the [src] with \the [W]."),\
+		span("danger", "You start cutting through \the [src] with \the [W]."))
+		playsound(src, W.usesound, 50, 1)
+
+		if(do_after(user, CUT_TIME * W.toolspeed, target = src))
+			if(current_stage == hole_size)
+				switch(++hole_size)
+					if(MEDIUM_HOLE)
+						visible_message(span("notice", "\The [user] cuts into \the [src] some more."))
+						to_chat(user, span("notice", "You could probably fit yourself through that hole now. Although climbing through would be much faster if you made it even bigger."))
+						climbable = TRUE
+					if(LARGE_HOLE)
+						visible_message(span("notice", "\The [user] completely cuts through \the [src]."))
+						to_chat(user, span("notice", "The hole in \the [src] is now big enough to walk through."))
+						climbable = FALSE
+				update_cut_status()
+	return TRUE
+
+/obj/structure/fence/proc/update_cut_status()
+	if(!cuttable)
+		return
+	density = TRUE
+
+	switch(hole_size)
+		if(NO_HOLE)
+			icon_state = initial(icon_state)
+		if(MEDIUM_HOLE)
+			icon_state = "straight_cut2"
+		if(LARGE_HOLE)
+			icon_state = "straight_cut3"
+			density = FALSE
+
+//FENCE DOORS
+
+/obj/structure/fence/door
+	name = "fence door"
+	desc = "Not very useful without a real lock."
+	icon_state = "door_closed"
+	cuttable = FALSE
+	var/open = FALSE
+	var/locked = FALSE
+
+/obj/structure/fence/door/Initialize()
+	update_door_status()
+	return ..()
+
+/obj/structure/fence/door/opened
+	icon_state = "door_opened"
+	open = TRUE
+	density = TRUE
+
+/obj/structure/fence/door/locked
+	desc = "It looks like it has a strong padlock attached."
+	locked = TRUE
+
+/obj/structure/fence/door/attack_hand(mob/user)
+	if(can_open(user))
+		toggle(user)
+	else
+		to_chat(user, span("warning", "\The [src] is [!open ? "locked" : "stuck open"]."))
+
+	return TRUE
+
+/obj/structure/fence/door/proc/toggle(mob/user)
+	switch(open)
+		if(FALSE)
+			visible_message(span("notice", "\The [user] opens \the [src]."))
+			open = TRUE
+		if(TRUE)
+			visible_message(span("notice", "\The [user] closes \the [src]."))
+			open = FALSE
+
+	update_door_status()
+	playsound(src, 'sound/machines/click.ogg', 100, 1)
+
+/obj/structure/fence/door/proc/update_door_status()
+	switch(open)
+		if(FALSE)
+			density = TRUE
+			icon_state = "door_closed"
+		if(TRUE)
+			density = FALSE
+			icon_state = "door_opened"
+
+/obj/structure/fence/door/proc/can_open(mob/user)
+	if(locked)
+		return FALSE
+	return TRUE
+
+#undef CUT_TIME
+#undef CLIMB_TIME
+
+#undef NO_HOLE
+#undef MEDIUM_HOLE
+#undef LARGE_HOLE
 #undef MAX_HOLE_SIZE

code/game/objects/structures/gravemarker.dm

@@ -38,15 +38,12 @@
 		if(epitaph)
 			to_chat(user, epitaph)
 
-/obj/structure/gravemarker/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(!mover)
-		return 1
+/obj/structure/gravemarker/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
+		return TRUE
 	if(get_dir(loc, target) & dir)
 		return !density
-	else
-		return 1
+	return TRUE
 
 /obj/structure/gravemarker/CheckExit(atom/movable/O as mob|obj, target as turf)
 	if(istype(O) && O.checkpass(PASSTABLE))

code/game/objects/structures/grille.dm

@@ -49,15 +49,12 @@
 
 	attack_generic(user,damage_dealt,attack_message)
 
-/obj/structure/grille/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0)) return 1
+/obj/structure/grille/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSGRILLE))
-		return 1
-	else
-		if(istype(mover, /obj/item/projectile))
-			return prob(30)
-		else
-			return !density
+		return TRUE
+	if(istype(mover, /obj/item/projectile))
+		return prob(30)
+	return !density
 
 /obj/structure/grille/bullet_act(var/obj/item/projectile/Proj)
 	if(!Proj)	return
@@ -235,14 +232,10 @@
 
 /obj/structure/grille/cult
 	name = "cult grille"
-	desc = "A matrice built out of an unknown material, with some sort of force field blocking air around it"
+	desc = "A matrice built out of an unknown material, with some sort of force field blocking air around it."
 	icon_state = "grillecult"
-	health = 40 //Make it strong enough to avoid people breaking in too easily
-
-/obj/structure/grille/cult/CanPass(atom/movable/mover, turf/target, height = 1.5, air_group = 0)
-	if(air_group)
-		return 0 //Make sure air doesn't drain
-	..()
+	health = 40 // Make it strong enough to avoid people breaking in too easily.
+	can_atmos_pass = ATMOS_PASS_NO // Make sure air doesn't drain.
 
 /obj/structure/grille/broken/cult
 	icon_state = "grillecult-b"

code/game/objects/structures/inflatable.dm

@@ -25,6 +25,7 @@
 	density = 1
 	anchored = 1
 	opacity = 0
+	can_atmos_pass = ATMOS_PASS_DENSITY
 
 	icon = 'icons/obj/inflatable.dmi'
 	icon_state = "wall"
@@ -40,9 +41,6 @@
 	update_nearby_tiles()
 	return ..()
 
-/obj/structure/inflatable/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	return 0
-
 /obj/structure/inflatable/bullet_act(var/obj/item/projectile/Proj)
 	var/proj_damage = Proj.get_structure_damage()
 	if(!proj_damage) return
@@ -168,9 +166,7 @@
 /obj/structure/inflatable/door/attack_hand(mob/user as mob)
 	return TryToSwitchState(user)
 
-/obj/structure/inflatable/door/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group)
-		return state
+/obj/structure/inflatable/door/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover, /obj/effect/beam))
 		return !opacity
 	return !density

code/game/objects/structures/plasticflaps.dm

@@ -64,15 +64,4 @@
 /obj/structure/plasticflaps/mining //A specific type for mining that doesn't allow airflow because of them damn crates
 	name = "airtight plastic flaps"
 	desc = "Heavy duty, airtight, plastic flaps."
-
-/obj/structure/plasticflaps/mining/New() //set the turf below the flaps to block air
-	var/turf/T = get_turf(loc)
-	if(T)
-		T.blocks_air = 1
-	..()
-
-/obj/structure/plasticflaps/mining/Destroy() //lazy hack to set the turf to allow air to pass if it's a simulated floor
-	var/turf/T = get_turf(loc)
-	if(T && istype(T, /turf/simulated/floor))
-		T.blocks_air = 0
-	..()
+	can_atmos_pass = ATMOS_PASS_NO

code/game/objects/structures/railing.dm

@@ -34,15 +34,12 @@
 	for(var/obj/structure/railing/R in orange(location, 1))
 		R.update_icon()
 
-/obj/structure/railing/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(!mover)
-		return 1
+/obj/structure/railing/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
-	if(get_dir(loc, target) == dir)
+		return TRUE
+	if(get_dir(mover, target) == turn(dir, 180))
 		return !density
-	else
-		return 1
+	return TRUE
 
 /obj/structure/railing/examine(mob/user)
 	. = ..()

code/game/objects/structures/simple_doors.dm

@@ -2,6 +2,7 @@
 	name = "door"
 	density = 1
 	anchored = 1
+	can_atmos_pass = ATMOS_PASS_DENSITY
 
 	icon = 'icons/obj/doors/material_doors.dmi'
 	icon_state = "metal"
@@ -63,8 +64,7 @@
 /obj/structure/simple_door/attack_hand(mob/user as mob)
 	return TryToSwitchState(user)
 
-/obj/structure/simple_door/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group) return 0
+/obj/structure/simple_door/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover, /obj/effect/beam))
 		return !opacity
 	return !density

code/game/objects/structures/stool_bed_chair_nest/bed.dm

@@ -69,11 +69,10 @@
 		name = "[material.display_name] [initial(name)]"
 		desc += " It's made of [material.use_name]."
 
-/obj/structure/bed/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/structure/bed/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
-	else
-		return ..()
+		return TRUE
+	return ..()
 
 /obj/structure/bed/ex_act(severity)
 	switch(severity)

code/game/objects/structures/windoor_assembly.dm

@@ -54,14 +54,12 @@ obj/structure/windoor_assembly/Destroy()
 /obj/structure/windoor_assembly/update_icon()
 	icon_state = "[facing]_[secure]windoor_assembly[state]"
 
-/obj/structure/windoor_assembly/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/structure/windoor_assembly/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSGLASS))
-		return 1
+		return TRUE
 	if(get_dir(loc, target) == dir) //Make sure looking at appropriate border
-		if(air_group) return 0
 		return !density
-	else
-		return 1
+	return TRUE
 
 /obj/structure/windoor_assembly/CheckExit(atom/movable/mover as mob|obj, turf/target as turf)
 	if(istype(mover) && mover.checkpass(PASSGLASS))

code/game/objects/structures/window.dm

@@ -3,6 +3,7 @@
 	desc = "A window."
 	icon = 'icons/obj/structures_vr.dmi' // VOREStation Edit - New icons
 	density = 1
+	can_atmos_pass = ATMOS_PASS_DENSITY
 	w_class = ITEMSIZE_NORMAL
 
 	layer = WINDOW_LAYER
@@ -129,7 +130,17 @@
 /obj/structure/window/blob_act()
 	take_damage(50)
 
+<<<<<<< HEAD
+//TODO: Make full windows a separate type of window.
+//Once a full window, it will always be a full window, so there's no point
+//having the same type for both.
+/obj/structure/window/proc/is_full_window()
+	return (dir == SOUTHWEST || dir == SOUTHEAST || dir == NORTHWEST || dir == NORTHEAST)
+
 /obj/structure/window/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+=======
+/obj/structure/window/CanPass(atom/movable/mover, turf/target)
+>>>>>>> 4122c65... Merge pull request #5947 from Neerti/bump_fixes
 	if(istype(mover) && mover.checkpass(PASSGLASS))
 		return TRUE
 	if(is_fulltile())
@@ -139,6 +150,12 @@
 	else
 		return TRUE
 
+
+/obj/structure/window/CanZASPass(turf/T, is_zone)
+	if(is_fulltile() || get_dir(T, loc) == turn(dir, 180)) // Make sure we're handling the border correctly.
+		return anchored ? ATMOS_PASS_NO : ATMOS_PASS_YES // If it's anchored, it'll block air.
+	return ATMOS_PASS_YES // Don't stop airflow from the other sides.
+
 /obj/structure/window/CheckExit(atom/movable/O as mob|obj, target as turf)
 	if(istype(O) && O.checkpass(PASSGLASS))
 		return 1

code/game/objects/structures/window_spawner.dm

@@ -10,6 +10,7 @@
 	density = 1
 	anchored = 1.0
 	pressure_resistance = 4*ONE_ATMOSPHERE
+	can_atmos_pass = ATMOS_PASS_NO
 	var/win_path = /obj/structure/window/basic
 	var/activated
 
@@ -22,7 +23,7 @@
 /obj/effect/wingrille_spawn/attack_generic()
 	activate()
 
-/obj/effect/wingrille_spawn/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
+/obj/effect/wingrille_spawn/CanPass(atom/movable/mover, turf/target)
 	return FALSE
 
 /obj/effect/wingrille_spawn/Initialize()

code/game/shuttle_engines.dm

@@ -9,13 +9,15 @@
 	density = 1
 	opacity = 0
 	anchored = 1
+	can_atmos_pass = ATMOS_PASS_NO
 
 	var/window_flags = 0 // Bitflags to indicate connected windows
 	var/wall_flags = 0 // Bitflags to indicate connected walls
 
-/obj/structure/shuttle/window/CanPass(atom/movable/mover, turf/target, height, air_group)
-	if(!height || air_group) return 0
-	else return ..()
+/obj/structure/shuttle/window/CanPass(atom/movable/mover, turf/target)
+	if(istype(mover) && mover.checkpass(PASSGLASS))
+		return TRUE
+	return ..()
 
 /obj/structure/shuttle/window/Initialize()
 	. = ..()

code/modules/blob/blob.dm

@@ -22,10 +22,8 @@
 	update_icon()
 	return ..(loc)
 
-/obj/effect/blob/CanPass(var/atom/movable/mover, vra/turf/target, var/height = 0, var/air_group = 0)
-	if(air_group || height == 0)
-		return 1
-	return 0
+/obj/effect/blob/CanPass(var/atom/movable/mover, vra/turf/target)
+	return FALSE
 
 /obj/effect/blob/ex_act(var/severity)
 	switch(severity)
@@ -207,5 +205,5 @@
 	else
 		icon_state = "blob_damaged"
 
-/obj/effect/blob/shield/CanPass(var/atom/movable/mover, var/turf/target, var/height = 0, var/air_group = 0)
+/obj/effect/blob/shield/CanPass(var/atom/movable/mover, var/turf/target)
 	return !density

code/modules/blob2/blobs/base_blob.dm

@@ -46,9 +46,8 @@ var/list/blobs = list()
 		color = null
 		set_light(0)
 
-/obj/structure/blob/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0))
-		return TRUE
+// Blob tiles are not actually dense so we need Special Code(tm).
+/obj/structure/blob/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSBLOB))
 		return TRUE
 	else if(istype(mover, /mob/living))
@@ -57,12 +56,9 @@ var/list/blobs = list()
 			return TRUE
 	else if(istype(mover, /obj/item/projectile))
 		var/obj/item/projectile/P = mover
-		if(P.firer && P.firer.faction == "blob")
+		if(istype(P.firer) && P.firer.faction == "blob")
 			return TRUE
-		return FALSE
-	else
-		return FALSE
-//	return ..()
+	return FALSE
 
 /obj/structure/blob/examine(mob/user)
 	..()
@@ -257,7 +253,7 @@ var/list/blobs = list()
 	if(!P)
 		return
 
-	if(P.firer && P.firer.faction == "blob")
+	if(istype(P.firer) && P.firer.faction == "blob")
 		return
 
 	var/damage = P.get_structure_damage() // So tasers don't hurt the blob.

code/modules/blob2/blobs/shield.dm

@@ -6,6 +6,7 @@
 	desc = "A solid wall of slightly twitching tendrils."
 	max_integrity = 100
 	point_return = 4
+	can_atmos_pass = ATMOS_PASS_NO
 
 /obj/structure/blob/shield/core
 	point_return = 0

code/modules/holodeck/HolodeckObjects.dm

@@ -325,19 +325,18 @@
 		visible_message("<span class='notice'>[user] dunks [W] into the [src]!</span>", 3)
 		return
 
-/obj/structure/holohoop/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
+/obj/structure/holohoop/CanPass(atom/movable/mover, turf/target)
 	if (istype(mover,/obj/item) && mover.throwing)
 		var/obj/item/I = mover
 		if(istype(I, /obj/item/projectile))
-			return
+			return TRUE
 		if(prob(50))
-			I.loc = src.loc
-			visible_message("<span class='notice'>Swish! \the [I] lands in \the [src].</span>", 3)
+			I.forceMove(loc)
+			visible_message(span("notice", "Swish! \the [I] lands in \the [src]."), 3)
 		else
-			visible_message("<span class='warning'>\The [I] bounces off of \the [src]'s rim!</span>", 3)
-		return 0
-	else
-		return ..(mover, target, height, air_group)
+			visible_message(span("warning", "\The [I] bounces off of \the [src]'s rim!"), 3)
+		return FALSE
+	return ..()
 
 
 /obj/machinery/readybutton

code/modules/hydroponics/trays/tray.dm

@@ -217,13 +217,10 @@
 
 	..()
 
-/obj/machinery/portable_atmospherics/hydroponics/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0)) return 1
-
+/obj/machinery/portable_atmospherics/hydroponics/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
-	else
-		return 0
+		return TRUE
+	return FALSE
 
 /obj/machinery/portable_atmospherics/hydroponics/proc/check_health()
 	if(seed && !dead && health <= 0)

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

@@ -143,8 +143,8 @@
 		var/mob/observer/dead/M = src
 		M.manifest(user)
 
-/mob/observer/dead/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	return 1
+/mob/observer/dead/CanPass(atom/movable/mover, turf/target)
+	return TRUE
 /*
 Transfer_mind is there to check if mob is being deleted/not going to have a body.
 Works together with spawning an observer, noted above.

code/modules/mob/living/living_movement.dm

@@ -1,7 +1,4 @@
-/mob/CanPass(atom/movable/mover, turf/target, height, air_group)
-	if(air_group || (height == 0))
-		return TRUE
-
+/mob/CanPass(atom/movable/mover, turf/target)
 	if(ismob(mover))
 		var/mob/moving_mob = mover
 		if ((other_mobs && moving_mob.other_mobs))
@@ -10,3 +7,6 @@
 		var/obj/item/projectile/P = mover
 		return !P.can_hit_target(src, P.permutated, src == P.original, TRUE)
 	return (!mover.density || !density || lying)
+
+/mob/CanZASPass(turf/T, is_zone)
+	return ATMOS_PASS_YES

code/modules/power/antimatter/shielding.dm

@@ -74,9 +74,8 @@ proc/cardinalrange(var/center)
 	return
 
 
-/obj/machinery/am_shielding/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0))	return 1
-	return 0
+/obj/machinery/am_shielding/CanPass(atom/movable/mover, turf/target)
+	return FALSE
 
 
 /obj/machinery/am_shielding/process()

code/modules/power/fusion/fusion_particle_catcher.dm

@@ -37,7 +37,7 @@
 	update_icon()
 	return 0
 
-/obj/effect/fusion_particle_catcher/CanPass(var/atom/movable/mover, var/turf/target, var/height=0, var/air_group=0)
+/obj/effect/fusion_particle_catcher/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover, /obj/effect/accelerated_particle) || istype(mover, /obj/item/projectile/beam))
 		return !density
-	return 1
+	return TRUE

code/modules/power/turbine.dm

@@ -95,10 +95,8 @@
 		stat |= BROKEN
 
 // When anchored, don't let air past us.
-/obj/machinery/compressor/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
-	if(!height || air_group)
-		return !anchored
-	return !density
+/obj/machinery/compressor/CanZASPass(turf/T, is_zone)
+	return anchored ? ATMOS_PASS_NO : ATMOS_PASS_YES
 
 /obj/machinery/compressor/proc/locate_machinery()
 	if(turbine)

code/modules/recycling/disposal.dm

@@ -467,7 +467,7 @@
 		H.vent_gas(loc)
 		qdel(H)
 
-/obj/machinery/disposal/CanPass(atom/movable/mover, turf/target, height, air_group)
+/obj/machinery/disposal/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover, /obj/item/projectile))
 		return 1
 	if (istype(mover,/obj/item) && mover.throwing)
@@ -483,7 +483,7 @@
 				M.show_message("\The [I] bounces off of \the [src]'s rim!", 3)
 		return 0
 	else
-		return ..(mover, target, height, air_group)
+		return ..(mover, target)
 
 // virtual disposal object
 // travels through pipes in lieu of actual items

code/modules/shieldgen/directional_shield.dm

@@ -53,10 +53,8 @@
 		projector = null
 	return ..()
 
-/obj/effect/directional_shield/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0))
-		return TRUE
-	else if(istype(mover, /obj/item/projectile))
+/obj/effect/directional_shield/CanPass(atom/movable/mover, turf/target)
+	if(istype(mover, /obj/item/projectile))
 		var/obj/item/projectile/P = mover
 		if(istype(P, /obj/item/projectile/test)) // Turrets need to try to kill the shield and so their test bullet needs to penetrate.
 			return TRUE
@@ -64,8 +62,6 @@
 		var/bad_arc = reverse_direction(dir) // Arc of directions from which we cannot block.
 		if(check_shield_arc(src, bad_arc, P)) // This is actually for mobs but it will work for our purposes as well.
 			return FALSE
-		else
-			return TRUE
 	return TRUE
 
 /obj/effect/directional_shield/bullet_act(var/obj/item/projectile/P)

code/modules/shieldgen/emergency_shield.dm

@@ -7,6 +7,7 @@
 	opacity = 0
 	anchored = 1
 	unacidable = 1
+	can_atmos_pass = ATMOS_PASS_NO
 	var/const/max_health = 200
 	var/health = max_health //The shield can only take so much beating (prevents perma-prisons)
 	var/shield_generate_power = 7500	//how much power we use when regenerating
@@ -38,10 +39,6 @@
 	update_nearby_tiles()
 	..()
 
-/obj/machinery/shield/CanPass(atom/movable/mover, turf/target, height, air_group)
-	if(!height || air_group) return 0
-	else return ..()
-
 /obj/machinery/shield/attackby(obj/item/weapon/W as obj, mob/user as mob)
 	if(!istype(W)) return
 

code/modules/shieldgen/energy_field.dm

@@ -18,6 +18,7 @@
 	plane = MOB_PLANE
 	layer = ABOVE_MOB_LAYER
 	density = 0
+	can_atmos_pass = ATMOS_PASS_DENSITY
 	var/obj/machinery/shield_gen/my_gen = null
 	var/strength = 0 // in Renwicks
 	var/ticks_recovering = 10
@@ -103,15 +104,6 @@
 		update_icon()
 		update_nearby_tiles()
 
-/obj/effect/energy_field/CanPass(atom/movable/mover, turf/target, height=1.5, air_group = 0)
-	//Purpose: Determines if the object (or airflow) can pass this atom.
-	//Called by: Movement, airflow.
-	//Inputs: The moving atom (optional), target turf, "height" and air group
-	//Outputs: Boolean if can pass.
-
-	//return (!density || !height || air_group)
-	return !density
-
 /obj/effect/energy_field/update_icon(var/update_neightbors = 0)
 	overlays.Cut()
 	var/list/adjacent_shields_dir = list()

code/modules/shieldgen/sheldwallgen.dm

@@ -317,13 +317,9 @@
 	return
 
 
-/obj/machinery/shieldwall/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
-	if(air_group || (height==0)) return 1
-
+/obj/machinery/shieldwall/CanPass(atom/movable/mover, turf/target)
 	if(istype(mover) && mover.checkpass(PASSGLASS))
 		return prob(20)
-	else
-		if (istype(mover, /obj/item/projectile))
-			return prob(10)
-		else
-			return !src.density
+	if(istype(mover, /obj/item/projectile))
+		return prob(10)
+	return !density

code/modules/tables/interactions.dm

@@ -1,21 +1,25 @@
 
-/obj/structure/table/CanPass(atom/movable/mover, turf/target, height, air_group)
+<<<<<<< HEAD
+/obj/structure/table/CanPass(atom/movable/mover, turf/target, height=0, air_group=0)
 	if(air_group || (height==0)) return 1
+=======
+/obj/structure/table/CanPass(atom/movable/mover, turf/target)
+>>>>>>> 4122c65... Merge pull request #5947 from Neerti/bump_fixes
 	if(istype(mover,/obj/item/projectile))
 		return (check_cover(mover,target))
 	if (flipped == 1)
 		if (get_dir(loc, target) == dir)
 			return !density
 		else
-			return 1
+			return TRUE
 	if(istype(mover) && mover.checkpass(PASSTABLE))
-		return 1
+		return TRUE
 	if(locate(/obj/structure/table/bench) in get_turf(mover))
-		return 0
+		return FALSE
 	var/obj/structure/table/table = locate(/obj/structure/table) in get_turf(mover)
 	if(table && !table.flipped)
-		return 1
-	return 0
+		return TRUE
+	return FALSE
 
 //checks if projectile 'P' from turf 'from' can hit whatever is behind the table. Returns 1 if it can, 0 if bullet stops.
 /obj/structure/table/proc/check_cover(obj/item/projectile/P, turf/from)