/tg/ 4/14 (#367)

* outside code stuff

* defines, helpers, etc

* everything not module

* modules

* compiled fixes + missing sounds

code/modules/atmospherics/environmental/LINDA_turf_tile.dm

@@ -322,10 +322,10 @@
 
 	for(var/t in turf_list)
 		var/turf/open/T = t
-		if (space_is_all_consuming && !space_in_group && istype(T.air, /datum/gas_mixture/space))
+		if (space_is_all_consuming && !space_in_group && istype(T.air, /datum/gas_mixture/immutable/space))
 			space_in_group = 1
 			qdel(A)
-			A = new/datum/gas_mixture/space()
+			A = new/datum/gas_mixture/immutable/space()
 		A.merge(T.air)
 
 	for(var/id in A_gases)

code/modules/atmospherics/gasmixtures/immutable_mixtures.dm

@@ -0,0 +1,81 @@
+//"immutable" gas mixture used for immutable calculations
+//it can be changed, but any changes will ultimately be undone before they can have any effect
+
+/datum/gas_mixture/immutable
+	var/initial_temperature
+
+/datum/gas_mixture/immutable/proc/reset_gas_mix()
+	temperature = initial_temperature
+	temperature_archived = initial_temperature
+
+/datum/gas_mixture/immutable/New()
+	..()
+	reset_gas_mix()
+
+/datum/gas_mixture/immutable/garbage_collect()
+	reset_gas_mix()
+
+/datum/gas_mixture/immutable/archive()
+	return 1 //nothing changes, so we do nothing and the archive is successful
+
+/datum/gas_mixture/immutable/merge()
+	return 0 //we're immutable.
+
+/datum/gas_mixture/immutable/heat_capacity_archived()
+	return heat_capacity()
+
+/datum/gas_mixture/immutable/share(datum/gas_mixture/sharer, atmos_adjacent_turfs = 4)
+	. = ..(sharer, 0)
+	reset_gas_mix()
+
+/datum/gas_mixture/immutable/after_share()
+	temperature = initial_temperature
+	reset_gas_mix()
+
+/datum/gas_mixture/immutable/react()
+	return 0 //we're immutable.
+
+/datum/gas_mixture/immutable/copy()
+	return new type //we're immutable, so we can just return a new instance.
+
+/datum/gas_mixture/immutable/copy_from()
+	return 0 //we're immutable.
+
+/datum/gas_mixture/immutable/copy_from_turf()
+	return 0 //we're immutable.
+
+/datum/gas_mixture/immutable/parse_gas_string()
+	return 0 //we're immutable.
+
+/datum/gas_mixture/immutable/temperature_share(datum/gas_mixture/sharer, conduction_coefficient, sharer_temperature, sharer_heat_capacity)
+	. = ..()
+	temperature = initial_temperature
+
+//used by space tiles
+/datum/gas_mixture/immutable/space
+	initial_temperature = TCMB
+
+/datum/gas_mixture/immutable/space/garbage_collect()
+	gases.Cut() //clever way of ensuring we always are empty.
+
+/datum/gas_mixture/immutable/space/heat_capacity()
+	return 7000
+
+/datum/gas_mixture/immutable/space/remove()
+	return copy() //we're always empty, so we can just return a copy.
+
+/datum/gas_mixture/immutable/space/remove_ratio()
+	return copy() //we're always empty, so we can just return a copy.
+
+
+//used by cloners
+/datum/gas_mixture/immutable/cloner
+	initial_temperature = T20C
+
+/datum/gas_mixture/immutable/cloner/reset_gas_mix()
+	assert_gas("n2")
+	gases["n2"][MOLES] = MOLES_O2STANDARD + MOLES_N2STANDARD
+	..()
+
+/datum/gas_mixture/immutable/cloner/heat_capacity()
+	return (MOLES_O2STANDARD + MOLES_N2STANDARD)*20 //specific heat of nitrogen is 20