Wolves with a den, fishing, and a mixed diet

Wolves
- Den: a boulder cave at the foot of the rim, sited from the seed (away
  from the sea and spawn, mouth toward the valley, clearing in front)
- Grace period: no wolves days 1-2; they move in on day 3 and howl; hunting
  from night 4; pack of 2, 3 from day 6, 4 from day 9; replaced by day
- Wary pack hunters: circle and dart in one at a time; a lit campfire is a
  safe zone, a torch makes them hesitate, walls block bites (line of
  sight); hit one and the pack turns; hurt wolves flee; a lone wolf is
  timid; by day they defend the den; home at dawn
- Glowing eyes, synthesised howls, can't sleep with wolves prowling
- Wolf pelt and Wolf Cloak (+25 warmth)
- Animals take a committed detour around obstacles

Fishing
- Fishing rod (workbench); cast a float onto the lake, 1.5 s to land a bite
- Perch and rarer trout; faster bites at dawn/dusk and in rain; grill them
- Visible fish near the shore that jump with splash rings

Mixed diet
- Foods belong to meat, fish or greens; each level runs down over ~1.5 days
- One group low: no healing; two low: Malnourished (health drains);
  all three good: Balanced diet (heal x1.5); HUD diet bars; saved

Tests: test_wolves and test_fishing_diet; run_all.sh covers 9 suites

scripts/player/survival.gd

@@ -42,6 +42,35 @@ var _hurt_cd := 0.0          ## no natural healing for a few seconds after a hit
 signal hurt(amount: float, from: Vector3)
 const HURT_NO_REGEN := 6.0
 
+## Mixed diet: each food group (meat, fish, greens) has a level that runs
+## down over about a day and a half. Food from a group tops it up.
+## - One group low: you don't heal naturally ("Poor diet").
+## - Two or more low: Malnourished. Health slowly drains, stamina recovers
+##   slower. Living on berries alone will kill you.
+## - All three kept up: Balanced diet, healing x1.5.
+const DIET_GROUPS := ["meat", "fish", "plants"]
+const DIET_NAMES := {"meat": "meat", "fish": "fish", "plants": "greens"}
+const DIET_DRAIN := 100.0 / 1800.0
+const DIET_LOW := 15.0
+const DIET_GOOD := 40.0
+const DIET_START := 60.0
+const MALNOURISHED_DRAIN := 0.12
+var diet := {"meat": DIET_START, "fish": DIET_START, "plants": DIET_START}
+
+## The groups that are running low right now.
+func diet_lacking() -> Array:
+	var out := []
+	for g in DIET_GROUPS:
+		if float(diet[g]) < DIET_LOW:
+			out.append(g)
+	return out
+
+func balanced_diet() -> bool:
+	for g in DIET_GROUPS:
+		if float(diet[g]) < DIET_GOOD:
+			return false
+	return true
+
 var player: CharacterBody3D
 var world: Node3D
 var _stamina_wait := 0.0
@@ -85,7 +114,13 @@ func step(dt: float) -> void:
 	if _stamina_wait > 0.0:
 		_stamina_wait -= dt
 	else:
-		stamina = minf(stamina + STAMINA_REGEN * (1.5 if rested > 0.0 else 1.0) * buff_mult("stamina_regen") * dt, MAX)
+		var malnourished := diet_lacking().size() >= 2
+		stamina = minf(stamina + STAMINA_REGEN * (1.5 if rested > 0.0 else 1.0) * buff_mult("stamina_regen")
+			* (0.7 if malnourished else 1.0) * dt, MAX)
+
+	for g in DIET_GROUPS:
+		diet[g] = maxf(float(diet[g]) - DIET_DRAIN * dt, 0.0)
+	var lacking := diet_lacking()
 
 	for id in buffs.keys():
 		buffs[id].left -= dt
@@ -98,10 +133,13 @@ func step(dt: float) -> void:
 		dmg += 0.6
 	if warmth < 12.0:
 		dmg += 0.5
+	if lacking.size() >= 2:
+		dmg += MALNOURISHED_DRAIN
 	if dmg > 0.0:
 		health = maxf(health - dmg * dt, 0.0)
-	elif hunger > 40.0 and warmth > 35.0 and _hurt_cd <= 0.0:
-		health = minf(health + 0.5 * buff_mult("health_regen") * dt, MAX)
+	elif hunger > 40.0 and warmth > 35.0 and _hurt_cd <= 0.0 and lacking.is_empty():
+		var diet_mult := 1.5 if balanced_diet() else 1.0
+		health = minf(health + 0.5 * buff_mult("health_regen") * diet_mult * dt, MAX)
 
 	_update_statuses()
 	changed.emit()
@@ -123,6 +161,14 @@ func _update_statuses() -> void:
 		statuses.append("Hungry")
 	if wet > 0.0:
 		statuses.append("Wet")
+	var lacking := diet_lacking()
+	if not lacking.is_empty():
+		var need: Array[String] = []
+		for g in lacking:
+			need.append(DIET_NAMES[g])
+		statuses.append("%s (need %s)" % ["Malnourished" if lacking.size() >= 2 else "Poor diet", ", ".join(need)])
+	elif balanced_diet():
+		statuses.append("Balanced diet")
 	if sheltered:
 		statuses.append("Sheltered")
 	if rested > 0.0:
@@ -145,6 +191,11 @@ func eat(food: Dictionary) -> void:
 	health = clampf(health + float(food.get("health", 0)), minf(health, 1.0), MAX)
 	if food.has("buff"):
 		add_buff(food.buff)
+	var d: Dictionary = food.get("diet", {})
+	for g in d:
+		if diet.has(g):
+			diet[g] = minf(float(diet[g]) + float(d[g]), MAX)
+	_update_statuses()
 	changed.emit()
 
 func soak() -> void:
@@ -168,6 +219,9 @@ func reset_after_death() -> void:
 	warmth = 60.0
 	wet = 0.0
 	buffs.clear()
+	# Don't respawn straight back into malnutrition.
+	for g in DIET_GROUPS:
+		diet[g] = maxf(float(diet[g]), 30.0)
 	changed.emit()
 
 ## Takes a hit (a boar, later wolves). Pauses natural healing briefly.
@@ -198,7 +252,7 @@ func add_buff(b: Dictionary) -> void:
 
 func to_data() -> Dictionary:
 	return {"health": health, "stamina": stamina, "hunger": hunger, "warmth": warmth, "wet": wet, "rested": rested,
-		"buffs": buffs.duplicate(true)}
+		"buffs": buffs.duplicate(true), "diet": diet.duplicate()}
 
 func load_data(d: Dictionary) -> void:
 	health = float(d.get("health", health))
@@ -208,5 +262,9 @@ func load_data(d: Dictionary) -> void:
 	wet = float(d.get("wet", 0.0))
 	rested = float(d.get("rested", 0.0))
 	buffs = (d.get("buffs", {}) as Dictionary).duplicate(true)
+	# Older saves have no diet: start it where a new world does.
+	var sd: Dictionary = d.get("diet", {})
+	for g in DIET_GROUPS:
+		diet[g] = float(sd.get(g, DIET_START))
 	dead = false
 	changed.emit()