New Limb HUD System, from Bay

Manually ports https://github.com/Baystation12/Baystation12/pull/13530, and https://github.com/Baystation12/Baystation12/pull/13561 from bay.
Adjusts the scaling on the coloration, since it seems Bay has different shading than us for species, otherwise some species would be dark, and others would be superbright.
Credit goes to Zuhayr for the code.

code/modules/mob/death.dm

@@ -74,6 +74,7 @@
 	drop_l_hand()
 
 	if(healths)
+		healths.overlays = null // This is specific to humans but the relevant code is here; shouldn't mess with other mobs.
 		healths.icon_state = "health6"
 
 	timeofdeath = world.time

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

@@ -1032,37 +1032,38 @@
 		var/obj/machinery/camera/cam = client.eye
 		client.screen |= cam.client_huds
 
-	if(stat == UNCONSCIOUS && health <= 0)
-		//Critical damage passage overlay
-		var/severity = 0
-		switch(health)
-			if(-20 to -10)			severity = 1
-			if(-30 to -20)			severity = 2
-			if(-40 to -30)			severity = 3
-			if(-50 to -40)			severity = 4
-			if(-60 to -50)			severity = 5
-			if(-70 to -60)			severity = 6
-			if(-80 to -70)			severity = 7
-			if(-90 to -80)			severity = 8
-			if(-95 to -90)			severity = 9
-			if(-INFINITY to -95)	severity = 10
-		overlay_fullscreen("crit", /obj/screen/fullscreen/crit, severity)
-	else
-		clear_fullscreen("crit")
-		//Oxygen damage overlay
-		if(oxyloss)
+	if(stat != DEAD)
+		if(stat == UNCONSCIOUS && health <= 0)
+			//Critical damage passage overlay
 			var/severity = 0
-			switch(oxyloss)
-				if(10 to 20)		severity = 1
-				if(20 to 25)		severity = 2
-				if(25 to 30)		severity = 3
-				if(30 to 35)		severity = 4
-				if(35 to 40)		severity = 5
-				if(40 to 45)		severity = 6
-				if(45 to INFINITY)	severity = 7
-			overlay_fullscreen("oxy", /obj/screen/fullscreen/oxy, severity)
+			switch(health)
+				if(-20 to -10)			severity = 1
+				if(-30 to -20)			severity = 2
+				if(-40 to -30)			severity = 3
+				if(-50 to -40)			severity = 4
+				if(-60 to -50)			severity = 5
+				if(-70 to -60)			severity = 6
+				if(-80 to -70)			severity = 7
+				if(-90 to -80)			severity = 8
+				if(-95 to -90)			severity = 9
+				if(-INFINITY to -95)	severity = 10
+			overlay_fullscreen("crit", /obj/screen/fullscreen/crit, severity)
 		else
-			clear_fullscreen("oxy")
+			clear_fullscreen("crit")
+			//Oxygen damage overlay
+			if(oxyloss)
+				var/severity = 0
+				switch(oxyloss)
+					if(10 to 20)		severity = 1
+					if(20 to 25)		severity = 2
+					if(25 to 30)		severity = 3
+					if(30 to 35)		severity = 4
+					if(35 to 40)		severity = 5
+					if(40 to 45)		severity = 6
+					if(45 to INFINITY)	severity = 7
+				overlay_fullscreen("oxy", /obj/screen/fullscreen/oxy, severity)
+			else
+				clear_fullscreen("oxy")
 
 		//Fire and Brute damage overlay (BSSR)
 		var/hurtdamage = src.getBruteLoss() + src.getFireLoss() + damageoverlaytemp
@@ -1138,19 +1139,37 @@
 			if (analgesic > 100)
 				healths.icon_state = "health_numb"
 			else
-				switch(hal_screwyhud)
-					if(1)	healths.icon_state = "health6"
-					if(2)	healths.icon_state = "health7"
-					else
-						//switch(health - halloss)
-						switch(100 - (!can_feel_pain() ? 0 : traumatic_shock))
-							if(100 to INFINITY)		healths.icon_state = "health0"
-							if(80 to 100)			healths.icon_state = "health1"
-							if(60 to 80)			healths.icon_state = "health2"
-							if(40 to 60)			healths.icon_state = "health3"
-							if(20 to 40)			healths.icon_state = "health4"
-							if(0 to 20)				healths.icon_state = "health5"
-							else					healths.icon_state = "health6"
+				// Generate a by-limb health display.
+				healths.icon_state = "blank"
+				healths.overlays = null
+
+				var/no_damage = 1
+				var/trauma_val = 0 // Used in calculating softcrit/hardcrit indicators.
+				if(!(species.flags & NO_PAIN))
+					trauma_val = max(traumatic_shock,halloss)/species.total_health
+				var/limb_trauma_val = trauma_val*0.3
+				// Collect and apply the images all at once to avoid appearance churn.
+				var/list/health_images = list()
+				for(var/obj/item/organ/external/E in organs)
+					if(no_damage && (E.brute_dam || E.burn_dam))
+						no_damage = 0
+					health_images += E.get_damage_hud_image(limb_trauma_val)
+
+				// Apply a fire overlay if we're burning.
+				if(on_fire)
+					health_images += image('icons/mob/screen1_health.dmi',"burning")
+
+				// Show a general pain/crit indicator if needed.
+				if(trauma_val)
+					if(!(species.flags & NO_PAIN))
+						if(trauma_val > 0.7)
+							health_images += image('icons/mob/screen1_health.dmi',"softcrit")
+						if(trauma_val >= 1)
+							health_images += image('icons/mob/screen1_health.dmi',"hardcrit")
+				else if(no_damage)
+					health_images += image('icons/mob/screen1_health.dmi',"fullhealth")
+
+				healths.overlays += health_images
 
 		if(nutrition_icon)
 			switch(nutrition)

code/modules/mob/living/carbon/human/species/species.dm

@@ -108,6 +108,7 @@
 	// HUD data vars.
 	var/datum/hud_data/hud
 	var/hud_type
+	var/health_hud_intensity = 1  // This modifies how intensely the health hud is colored.
 
 	// Body/form vars.
 	var/list/inherent_verbs 	  // Species-specific verbs.

code/modules/mob/living/carbon/human/species/station/monkey.dm

@@ -14,6 +14,7 @@
 	mob_size = MOB_SMALL
 	has_fine_manipulation = 0
 	show_ssd = null
+	health_hud_intensity = 2
 
 	gibbed_anim = "gibbed-m"
 	dusted_anim = "dust-m"

code/modules/mob/living/carbon/human/species/station/prometheans.dm

@@ -23,6 +23,7 @@ var/datum/species/shapeshifter/promethean/prometheans
 	flags =            NO_SCAN | NO_SLIP | NO_MINOR_CUT
 	appearance_flags = HAS_SKIN_COLOR | HAS_EYE_COLOR | HAS_HAIR_COLOR | RADIATION_GLOWS
 	spawn_flags =      SPECIES_IS_RESTRICTED
+	health_hud_intensity = 2
 
 	breath_type = null
 	poison_type = null

code/modules/mob/living/carbon/human/species/station/seromi.dm

@@ -11,6 +11,7 @@
 	name_language = "Schechi"
 	min_age = 12
 	max_age = 45
+	health_hud_intensity = 3
 
 	blood_color = "#D514F7"
 	flesh_color = "#5F7BB0"

code/modules/mob/living/carbon/human/species/station/station.dm

@@ -13,6 +13,7 @@
 	name_language = null // Use the first-name last-name generator rather than a language scrambler
 	min_age = 17
 	max_age = 110
+	health_hud_intensity = 1.5
 
 	spawn_flags = SPECIES_CAN_JOIN
 	appearance_flags = HAS_HAIR_COLOR | HAS_SKIN_TONE | HAS_LIPS | HAS_UNDERWEAR | HAS_EYE_COLOR
@@ -36,6 +37,7 @@
 	num_alternate_languages = 2
 	secondary_langs = list("Sinta'unathi")
 	name_language = "Sinta'unathi"
+	health_hud_intensity = 2.5
 
 	min_age = 18
 	max_age = 60
@@ -96,6 +98,7 @@
 	num_alternate_languages = 2
 	secondary_langs = list("Siik'tajr")
 	name_language = "Siik'tajr"
+	health_hud_intensity = 2.5
 
 	min_age = 17
 	max_age = 80
@@ -151,6 +154,7 @@
 	num_alternate_languages = 2
 	secondary_langs = list("Skrellian", "Schechi")
 	name_language = "Skrellian"
+	health_hud_intensity = 2
 
 	min_age = 19
 	max_age = 80
@@ -193,6 +197,7 @@
 	show_ssd = "completely quiescent"
 	num_alternate_languages = 1
 	name_language = "Rootspeak"
+	health_hud_intensity = 2.5
 
 	min_age = 1
 	max_age = 300