what a gas

code/modules/atmospherics/environmental/LINDA_fire.dm

@@ -139,7 +139,7 @@
 		add_overlay(lightning_overlay)
 	if(temperature > 4500000) //This is where noblium happens. Some fusion-y effects.
 		var/fusion_amt = temperature < LERP(4500000,12000000,0.5) ? gauss_lerp(temperature, 4500000, 12000000) : 1
-		var/mutable_appearance/fusion_overlay = mutable_appearance('icons/effects/tile_effects.dmi', "chem_gas")
+		var/mutable_appearance/fusion_overlay = mutable_appearance('icons/effects/atmospherics.dmi', "fusion_gas")
 		fusion_overlay.blend_mode = BLEND_ADD
 		fusion_overlay.alpha = fusion_amt * 255
 		var/mutable_appearance/rainbow_overlay = mutable_appearance('icons/mob/screen_gen.dmi', "druggy")

code/modules/atmospherics/environmental/LINDA_turf_tile.dm

@@ -113,17 +113,18 @@
 
 /turf/open/proc/tile_graphic()
 	var/static/list/nonoverlaying_gases = typecache_of_gases_with_no_overlays()
-	if(air)
-		. = new /list
-		var/list/gases = air.gases
-		for(var/id in gases)
-			if (nonoverlaying_gases[id])
-				continue
-			var/gas = gases[id]
-			var/gas_meta = gas[GAS_META]
-			var/gas_overlay = gas_meta[META_GAS_OVERLAY]
-			if(gas_overlay && gas[MOLES] > gas_meta[META_GAS_MOLES_VISIBLE])
-				. += gas_overlay
+	if(!air)
+		return
+	. = new /list
+	var/list/gases = air.gases
+	for(var/id in gases)
+		if (nonoverlaying_gases[id])
+			continue
+		var/gas = gases[id]
+		var/gas_meta = gas[GAS_META]
+		var/gas_overlay = gas_meta[META_GAS_OVERLAY]
+		if(gas_overlay && gas[MOLES] > gas_meta[META_GAS_MOLES_VISIBLE])
+			. += gas_overlay[min(FACTOR_GAS_VISIBLE_MAX, CEILING(gas[MOLES] / MOLES_GAS_VISIBLE_STEP, 1))]
 
 /proc/typecache_of_gases_with_no_overlays()
 	. = list()

code/modules/atmospherics/gasmixtures/gas_mixture.dm

@@ -86,13 +86,6 @@ GLOBAL_LIST_INIT(gaslist_cache, init_gaslist_cache())
 	if(!.)
 		. += HEAT_CAPACITY_VACUUM //we want vacuums in turfs to have the same heat capacity as space
 
-//prefer this in performance critical areas
-#define TOTAL_MOLES(cached_gases, out_var)\
-	out_var = 0;\
-	for(var/total_moles_id in cached_gases){\
-		out_var += cached_gases[total_moles_id][MOLES];\
-	}
-
 /datum/gas_mixture/proc/total_moles()
 	var/cached_gases = gases
 	TOTAL_MOLES(cached_gases, .)

code/modules/atmospherics/gasmixtures/gas_types.dm

@@ -11,7 +11,9 @@ GLOBAL_LIST_INIT(nonreactive_gases, typecacheof(list(/datum/gas/oxygen, /datum/g
 		gas_info[META_GAS_NAME] = initial(gas.name)
 		gas_info[META_GAS_MOLES_VISIBLE] = initial(gas.moles_visible)
 		if(initial(gas.moles_visible) != null)
-			gas_info[META_GAS_OVERLAY] = new /obj/effect/overlay/gas(initial(gas.gas_overlay))
+			gas_info[META_GAS_OVERLAY] = new /list(FACTOR_GAS_VISIBLE_MAX)
+			for(var/i in 1 to FACTOR_GAS_VISIBLE_MAX)
+				gas_info[META_GAS_OVERLAY][i] = new /obj/effect/overlay/gas(initial(gas.gas_overlay), i * 255 / FACTOR_GAS_VISIBLE_MAX)
 		gas_info[META_GAS_FUSION_POWER] = initial(gas.fusion_power)
 		gas_info[META_GAS_DANGER] = initial(gas.dangerous)
 		gas_info[META_GAS_ID] = initial(gas.id)
@@ -39,7 +41,7 @@ GLOBAL_LIST_INIT(nonreactive_gases, typecacheof(list(/datum/gas/oxygen, /datum/g
 	var/id = ""
 	var/specific_heat = 0
 	var/name = ""
-	var/gas_overlay = "" //icon_state in icons/effects/tile_effects.dmi
+	var/gas_overlay = "" //icon_state in icons/effects/atmospherics.dmi
 	var/moles_visible = null
 	var/dangerous = FALSE //currently used by canisters
 	var/fusion_power = 0 //How much the gas accelerates a fusion reaction
@@ -89,7 +91,7 @@ GLOBAL_LIST_INIT(nonreactive_gases, typecacheof(list(/datum/gas/oxygen, /datum/g
 	specific_heat = 40
 	name = "Nitrous Oxide"
 	gas_overlay = "nitrous_oxide"
-	moles_visible = 1
+	moles_visible = MOLES_GAS_VISIBLE * 2
 	dangerous = TRUE
 
 /datum/gas/nitryl
@@ -137,12 +139,13 @@ GLOBAL_LIST_INIT(nonreactive_gases, typecacheof(list(/datum/gas/oxygen, /datum/g
 	moles_visible = MOLES_GAS_VISIBLE * 60
 
 /obj/effect/overlay/gas
-	icon = 'icons/effects/tile_effects.dmi'
+	icon = 'icons/effects/atmospherics.dmi'
 	mouse_opacity = MOUSE_OPACITY_TRANSPARENT
 	anchored = TRUE  // should only appear in vis_contents, but to be safe
 	layer = FLY_LAYER
 	appearance_flags = TILE_BOUND
 
-/obj/effect/overlay/gas/New(state)
+/obj/effect/overlay/gas/New(state, alph)
 	. = ..()
 	icon_state = state
+	alpha = alph

code/modules/flufftext/Hallucination.dm

@@ -150,7 +150,7 @@ GLOBAL_LIST_INIT(hallucination_list, list(
 	var/turf/center
 	var/list/flood_images = list()
 	var/list/turf/flood_turfs = list()
-	var/image_icon = 'icons/effects/tile_effects.dmi'
+	var/image_icon = 'icons/effects/atmospherics.dmi'
 	var/image_state = "plasma"
 	var/radius = 0
 	var/next_expand = 0