Simplify slime temperature damage

Currently the damage-temperature curve is not continuous and isn't monotone.
It's better to change it to constant 30 damage between -50°C and 50K.
The exact shape of the function is not that important, because the slimes
resistance is mostly due to its bodytemperature need time to change.

code/modules/mob/living/carbon/metroid/life.dm

@@ -54,11 +54,13 @@
 
 	if(bodytemperature < (T0C + 5)) // start calculating temperature damage etc
 
-		if(bodytemperature <= (T0C - 50)) // hurt temperature
-			if(bodytemperature <= 50) // sqrting negative numbers is bad
+		if(bodytemperature <= hurt_temperature)
+			if(bodytemperature <= die_temperature)
 				adjustToxLoss(200)
 			else
-				adjustToxLoss(round(sqrt(bodytemperature)) * 2)
+				// could be more fancy, but doesn't worth the complexity: when the slimes goes into a cold area
+				// the damage is mostly determined by how fast its body cools
+				adjustToxLoss(30)
 
 	updatehealth()
 
@@ -547,4 +549,4 @@
 	return 0
 
 /mob/living/carbon/slime/slip() //Can't slip something without legs.
-	return 0
+	return 0

code/modules/mob/living/carbon/metroid/metroid.dm

@@ -49,6 +49,9 @@
 	var/SStun = 0 // NPC stun variable. Used to calm them down when they are attacked while feeding, or they will immediately re-attach
 	var/Discipline = 0 // if a slime has been hit with a freeze gun, or wrestled/attacked off a human, they become disciplined and don't attack anymore for a while. The part about freeze gun is a lie
 
+	var/hurt_temperature = T0C-50 // slime keeps taking damage when its bodytemperature is below this
+	var/die_temperature = 50 // slime dies instantly when its bodytemperature is below this
+
 	///////////TIME FOR SUBSPECIES
 
 	var/colour = "grey"
@@ -411,4 +414,4 @@
 /mob/living/carbon/slime/cannot_use_vents()
 	if(Victim)
 		return "You cannot ventcrawl while feeding."
-	..()
+	..()