Merge pull request #9518 from Ghommie/Ghommie-cit243

Ports "You can now click on objects and mobs below flaps and signs"

code/game/objects/structures/holosign.dm

@@ -9,11 +9,13 @@
 	armor = list("melee" = 0, "bullet" = 50, "laser" = 50, "energy" = 50, "bomb" = 0, "bio" = 0, "rad" = 0, "fire" = 20, "acid" = 20)
 	var/obj/item/holosign_creator/projector
 
-/obj/structure/holosign/New(loc, source_projector)
+/obj/structure/holosign/Initialize(mapload, source_projector)
+	. = ..()
 	if(source_projector)
 		projector = source_projector
 		projector.signs += src
-	..()
+	alpha = 0
+	SSvis_overlays.add_vis_overlay(src, icon, icon_state, ABOVE_MOB_LAYER, plane, dir, add_appearance_flags = RESET_ALPHA) //you see mobs under it, but you hit them like they are above it
 
 /obj/structure/holosign/Destroy()
 	if(projector)
@@ -71,10 +73,8 @@
 	desc = "A holographic barrier resembling a firelock. Though it does not prevent solid objects from passing through, gas is kept out."
 	icon_state = "holo_firelock"
 	density = FALSE
-	layer = ABOVE_MOB_LAYER
 	anchored = TRUE
 	CanAtmosPass = ATMOS_PASS_NO
-	layer = ABOVE_MOB_LAYER
 	alpha = 150
 
 /obj/structure/holosign/barrier/atmos/Initialize()
@@ -100,7 +100,6 @@
 	desc = "A holobarrier that uses biometrics to detect human viruses. Denies passing to personnel with easily-detected, malicious viruses. Good for quarantines."
 	icon_state = "holo_medical"
 	alpha = 125 //lazy :)
-	layer = ABOVE_MOB_LAYER
 	var/force_allaccess = FALSE
 	var/buzzcd = 0
 

code/game/objects/structures/plasticflaps.dm

@@ -6,12 +6,16 @@
 	armor = list("melee" = 100, "bullet" = 80, "laser" = 80, "energy" = 100, "bomb" = 50, "bio" = 100, "rad" = 100, "fire" = 50, "acid" = 50)
 	density = FALSE
 	anchored = TRUE
-	layer = ABOVE_MOB_LAYER
 	CanAtmosPass = ATMOS_PASS_NO
 
 /obj/structure/plasticflaps/opaque
 	opacity = TRUE
 
+/obj/structure/plasticflaps/Initialize()
+	. = ..()
+	alpha = 0
+	SSvis_overlays.add_vis_overlay(src, icon, icon_state, ABOVE_MOB_LAYER, plane, dir, add_appearance_flags = RESET_ALPHA) //you see mobs under it, but you hit them like they are above it
+
 /obj/structure/plasticflaps/examine(mob/user)
 	. = ..()
 	if(anchored)