From ddf41217cafa8298f6675bc2657db65355263715 Mon Sep 17 00:00:00 2001
From: Claude Code <claude@anthropic.com>
Date: Wed, 25 Mar 2026 23:53:21 -0700
Subject: [PATCH] =?UTF-8?q?feat(climate):=20=E2=9C=A8=20Add=20ecological?=
 =?UTF-8?q?=20event=20handlers=20and=20evaluation=20utilities=20for=20enha?=
 =?UTF-8?q?nced=20climate=20simulation?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>
---
 engine/src/modules/climate/atmosphere.gd      |   6 +-
 engine/src/modules/climate/climate.gd         |  15 +-
 engine/src/modules/climate/climate_base.gd    | 206 +++---------------
 .../src/modules/climate/climate_spec_eval.gd  |   9 +-
 .../climate/ecological_event_handlers_a.gd    |  49 ++---
 .../climate/ecological_event_handlers_b.gd    |  48 ++--
 .../modules/climate/ecological_event_utils.gd |   8 +-
 7 files changed, 91 insertions(+), 250 deletions(-)

diff --git a/engine/src/modules/climate/atmosphere.gd b/engine/src/modules/climate/atmosphere.gd
index 73958a44..6dfffe73 100644
--- a/engine/src/modules/climate/atmosphere.gd
+++ b/engine/src/modules/climate/atmosphere.gd
@@ -209,7 +209,7 @@ func _step4_humidity(game_map: RefCounted) -> void:
 			hum += ocean_evap * tile.temperature
 		else:
 			hum += soil_rate * tile.moisture
-			match tile.terrain_id:
+			match tile.biome_id:
 				"forest", "enchanted_forest":
 					hum += forest_et
 				"jungle":
@@ -251,7 +251,7 @@ func _is_windward_of_mountain(tile: Variant, game_map: RefCounted) -> bool:
 	var downwind_tile: Variant = game_map.get_tile(downwind_pos)
 	if downwind_tile == null:
 		return false
-	return downwind_tile.terrain_id == "mountains" or downwind_tile.elevation > 0.8
+	return downwind_tile.biome_id == "mountains" or downwind_tile.elevation > 0.8
 
 
 func _is_leeward_of_mountain(tile: Variant, game_map: RefCounted) -> bool:
@@ -261,7 +261,7 @@ func _is_leeward_of_mountain(tile: Variant, game_map: RefCounted) -> bool:
 	var upwind_tile: Variant = game_map.get_tile(upwind_pos)
 	if upwind_tile == null:
 		return false
-	return upwind_tile.terrain_id == "mountains" or upwind_tile.elevation > 0.8
+	return upwind_tile.biome_id == "mountains" or upwind_tile.elevation > 0.8
 
 
 # -----------------------------------------------------------------------
diff --git a/engine/src/modules/climate/climate.gd b/engine/src/modules/climate/climate.gd
index cc8e8bae..49027bd8 100644
--- a/engine/src/modules/climate/climate.gd
+++ b/engine/src/modules/climate/climate.gd
@@ -38,8 +38,7 @@ func process_turn(game_map: RefCounted, turn: int = 0, seed: int = 42) -> void:
 	_update_lake_evaporation(game_map)
 	_update_deep_earth_water(game_map)
 	_update_precipitation(game_map)
-	_check_terrain_evolution(game_map)
-	_update_corruption(game_map)
+	# Quality evolution removed — now owned by ecosystem.gd
 	_tick_ley_residue(game_map)
 	EcologicalEventsScript.process_events(
 		game_map, turn, seed, _spec, DataLoader.get_ecological_events()
@@ -167,7 +166,7 @@ func _update_lake_evaporation(game_map: RefCounted) -> void:
 
 	for axial: Vector2i in game_map.tiles:
 		var tile: Variant = game_map.tiles[axial]
-		var tid: String = tile.terrain_id
+		var tid: String = tile.biome_id
 		if tid != "lake" and tid != "ocean" and tid != "coast":
 			continue
 
@@ -192,7 +191,7 @@ func _update_lake_evaporation(game_map: RefCounted) -> void:
 				var hop_tile: Variant = game_map.tiles.get(hop_pos)
 				if hop_tile == null:
 					break
-				var hop_tid: String = hop_tile.terrain_id
+				var hop_tid: String = hop_tile.biome_id
 				# Stop if we hit another water tile (no double-injection)
 				if hop_tid == "ocean" or hop_tid == "coast" or hop_tid == "lake":
 					break
@@ -225,7 +224,7 @@ func _update_deep_earth_water(game_map: RefCounted) -> void:
 	for axial: Vector2i in game_map.tiles:
 		var tile: Variant = game_map.tiles[axial]
 
-		if tile.terrain_id == "volcano":
+		if tile.biome_id == "volcano":
 			tile.moisture = clampf(tile.moisture + vol_self, 0.0, 1.0)
 			for nb_pos: Vector2i in HexUtilsScript.get_neighbors(axial):
 				var nb: Variant = game_map.tiles.get(nb_pos)
@@ -301,7 +300,7 @@ func _compute_global_stats(game_map: RefCounted) -> void:
 	var count: int = 0
 	for axial: Vector2i in game_map.tiles:
 		var tile: Variant = game_map.tiles[axial]
-		if tile.terrain_id != "ocean":
+		if tile.biome_id != "ocean":
 			total += tile.temperature
 			count += 1
 	global_avg_temp = total / float(count) if count > 0 else 0.5
@@ -316,7 +315,7 @@ func _compute_global_stats(game_map: RefCounted) -> void:
 	var dead_count: int = 0
 	for axial: Vector2i in game_map.tiles:
 		var tile: Variant = game_map.tiles[axial]
-		if tile.terrain_id != "coast":
+		if tile.biome_id != "coast":
 			continue
 		coast_count += 1
 		if tile.temperature > bleach_thresh:
@@ -381,7 +380,7 @@ func _ensure_ocean_dist(game_map: RefCounted) -> void:
 	# Seed BFS from all water tiles (distance 0)
 	var queue: Array[Vector2i] = []
 	for axial: Vector2i in game_map.tiles:
-		var tid: String = game_map.tiles[axial].terrain_id
+		var tid: String = game_map.tiles[axial].biome_id
 		if tid == "ocean" or tid == "coast" or tid == "lake" or tid == "inland_sea":
 			_ocean_dist_cache[axial] = 0
 			queue.append(axial)
diff --git a/engine/src/modules/climate/climate_base.gd b/engine/src/modules/climate/climate_base.gd
index 5dc0eb00..c20731db 100644
--- a/engine/src/modules/climate/climate_base.gd
+++ b/engine/src/modules/climate/climate_base.gd
@@ -19,26 +19,23 @@ const LeyNetworkScript: GDScript = preload("res://engine/src/modules/ley/ley_net
 # Fallback defaults — used only when climate_params.json absent (logs warning)
 const _DEFAULTS: Dictionary = {
 	"wind_conductivity": 0.1,
-	"energy_scale": 0.01,
-	"equilibrium_relaxation": 0.05,
+	"energy_scale": 0.005,
+	"equilibrium_relaxation": 0.08,
 	"evaporation_rate": 0.05,
 	"moisture_transport": 0.15,
 	"precipitation_threshold": 0.7,
-	"moisture_decay": 0.98,
-	"moisture_relaxation": 0.02,
-	"ocean_evaporation_hops": 3,
+	"moisture_decay": 0.995,
+	"moisture_relaxation": 0.04,
+	"ocean_evaporation_hops": 4,
 	"ocean_evaporation_hop_decay": 0.5,
-	"atmospheric_loss_rate": 0.001,
+	"atmospheric_loss_rate": 0.0003,
 	"quality_up_threshold": 10,
 	"quality_down_threshold": 5,
-	"corruption_spread_rate": 0.02,
-	"corruption_flip_threshold": 0.5,
-	"corruption_decay_rate": 0.004,
-	"corruption_heal_rate": 0.008,
-	"corruption_heal_threshold": 0.15,
 	"lake_thermal_conductivity": 0.05,
 	"river_moisture_transport": 0.075,
 	"mountain_rain_shadow_block": 0.9,
+	"solar_min": 0.15,
+	"solar_max": 0.70,
 }
 
 const _DEW_DEFAULTS: Dictionary = {
@@ -66,7 +63,7 @@ var _params: Dictionary = {}
 var _spec: Dictionary = {}
 var _params_loaded: bool = false
 
-# Per-terrain data cache (albedo, evapotranspiration) keyed by terrain_id string
+# Per-terrain data cache (albedo, evapotranspiration) keyed by biome_id string
 var _terrain_cache: Dictionary = {}
 
 # Ocean proximity cache: axial → int (hex distance to nearest water tile).
@@ -106,7 +103,7 @@ func _update_temperatures(game_map: RefCounted) -> void:
 		var solar: float = solar_by_row[clampi(offset.y, 0, h - 1)]
 		var current_temp: float = old_temp[axial]
 
-		var terrain_data: Dictionary = _get_terrain_data(tile.terrain_id)
+		var terrain_data: Dictionary = _get_terrain_data(tile.biome_id)
 		var albedo: float = terrain_data.get("albedo", 0.4)
 		var net_solar: float = solar * (1.0 - albedo) * energy_scale
 
@@ -141,7 +138,7 @@ func _update_lake_thermal_effects(game_map: RefCounted) -> void:
 
 	for axial: Vector2i in game_map.tiles:
 		var tile: Variant = game_map.tiles[axial]
-		if tile.terrain_id != "lake":
+		if tile.biome_id != "lake":
 			continue
 		var lake_temp: float = tile.temperature
 		for nb_pos: Vector2i in HexUtilsScript.get_neighbors(axial):
@@ -184,7 +181,7 @@ func _update_moisture_wind(game_map: RefCounted) -> void:
 		if old_moisture.has(upwind_pos):
 			var upwind_tile: Variant = game_map.tiles.get(upwind_pos)
 			var upwind_is_mountain: bool = (
-				upwind_tile != null and upwind_tile.terrain_id == "mountains"
+				upwind_tile != null and upwind_tile.biome_id == "mountains"
 			)
 			var block: float = rain_shadow_block if upwind_is_mountain else 0.0
 			transported = (
@@ -192,7 +189,7 @@ func _update_moisture_wind(game_map: RefCounted) -> void:
 			)
 
 		# Evapotranspiration and magic forcing are per-tile local effects — safe to add here
-		var terrain_data: Dictionary = _get_terrain_data(tile.terrain_id)
+		var terrain_data: Dictionary = _get_terrain_data(tile.biome_id)
 		var evapotrans: float = terrain_data.get("evapotranspiration", 0.0)
 
 		# Moisture equilibrium relaxation — pull toward climate baseline (like temperature)
@@ -223,179 +220,26 @@ func _update_moisture_wind(game_map: RefCounted) -> void:
 # -- Step 8: Terrain quality evolution --
 
 
-func _check_terrain_evolution(game_map: RefCounted) -> void:
-	var up_thresh: int = _params.get("quality_up_threshold", _DEFAULTS["quality_up_threshold"])
-	var down_thresh: int = _params.get(
-		"quality_down_threshold", _DEFAULTS["quality_down_threshold"]
-	)
-
-	for axial: Vector2i in game_map.tiles:
-		var tile: Variant = game_map.tiles[axial]
-		var tid: String = tile.terrain_id
-
-		# Natural wonders are geological formations — quality evolves but terrain doesn't flip
-		if tile.is_natural_wonder():
-			continue
-
-		# Water, corrupted, and fixed-form terrains don't evolve via climate
-		if (
-			tid == "ocean"
-			or tid == "coast"
-			or tid == "lake"
-			or tid == "corrupted_land"
-			or tid == "volcano"
-		):
-			continue
-
-		var ideal: String = _ideal_terrain(tile)
-
-		if ideal == tid:
-			tile.quality_progress += 1
-			if tile.quality_progress >= up_thresh:
-				tile.quality_progress = 0
-				if tile.quality < 5:
-					var old_q: int = tile.quality
-					tile.quality += 1
-					EventBus.quality_changed.emit(tile, old_q, tile.quality)
-		else:
-			tile.quality_progress -= 1
-			if tile.quality_progress <= -down_thresh:
-				tile.quality_progress = 0
-				if tile.quality > 1:
-					var old_q: int = tile.quality
-					tile.quality -= 1
-					EventBus.quality_changed.emit(tile, old_q, tile.quality)
-				else:
-					# Quality at floor — terrain flips one step along its chain
-					var old_type: String = tid
-					tile.terrain_id = ideal
-					tile.quality = 1
-					tile.quality_progress = 0
-					EventBus.terrain_transformed.emit(tile, old_type, ideal)
-
-
-# -- Step 9: Corruption spreading --
-
-
-func _update_corruption(game_map: RefCounted) -> void:
-	var spread_rate: float = _params.get(
-		"corruption_spread_rate", _DEFAULTS["corruption_spread_rate"]
-	)
-	var flip_threshold: float = _params.get(
-		"corruption_flip_threshold", _DEFAULTS["corruption_flip_threshold"]
-	)
-	var decay_rate: float = _params.get("corruption_decay_rate", _DEFAULTS["corruption_decay_rate"])
-	var heal_rate: float = _params.get("corruption_heal_rate", _DEFAULTS["corruption_heal_rate"])
-	var heal_threshold: float = _params.get(
-		"corruption_heal_threshold", _DEFAULTS["corruption_heal_threshold"]
-	)
-
-	# Accumulate pressure increments into a separate dict — one O(n) read pass,
-	# then one O(n) write pass. Avoids double-counting and in-place mutation.
-	var pressure_deltas: Dictionary = {}  # axial → float
-
-	for axial: Vector2i in game_map.tiles:
-		var tile: Variant = game_map.tiles[axial]
-		if tile.corruption_pressure <= 0.0:
-			continue
-		# terrain_power corruption_spread_modifier on the SOURCE tile scales spread rate.
-		# e.g. jungle = 0.5x (resists spread), swamp = 1.5x (accelerates spread).
-		var source_modifier: float = TerrainAffinityScript.get_corruption_spread_modifier(
-			tile.terrain_id
-		)
-		var base_spread: float = spread_rate * source_modifier
-		for nb_pos: Vector2i in HexUtilsScript.get_neighbors(axial):
-			if not game_map.tiles.has(nb_pos):
-				continue
-			var nb: Variant = game_map.tiles[nb_pos]
-			if nb.terrain_id == "corrupted_land":
-				continue
-			# Ley line channeling: spread rate is modified by the ley properties of the
-			# receiving tile. Death ley = 3x, generic ley edge = 2x,
-			# Nature/Life ley = 0.5x (resists). Off-ley = no channeling modifier.
-			var ley_mult: float = _ley_channeling_mult(nb)
-			# Moisture resistance: high-moisture terrain (jungle, swamp, water) resists
-			# corruption biologically. Marine life (fish, reefs, algae) can still carry
-			# corruption through water — so water isn't immune, just dampened.
-			var moisture_resist: float = 1.0 - nb.moisture * 0.4
-			# City protection buildings write corruption_resistance_pct to scale down spread
-			var corruption_resist: float = 1.0 - clampf(nb.corruption_resistance_pct, 0.0, 1.0)
-			pressure_deltas[nb_pos] = (
-				pressure_deltas.get(nb_pos, 0.0)
-				+ base_spread * ley_mult * moisture_resist * corruption_resist
-			)
-
-	# Apply pressure deltas + natural decay + Life/Nature ley active healing
-	for axial: Vector2i in game_map.tiles:
-		var tile: Variant = game_map.tiles[axial]
-		var incoming: float = pressure_deltas.get(axial, 0.0)
-
-		# Natural pressure decay — corruption dissipates without active feeding sources
-		var drain: float = decay_rate
-
-		# Life/Nature ley lines actively heal (bonus drain, capped at 3 stacks)
-		if tile.ley_line_count > 0 and (tile.ley_school == "life" or tile.ley_school == "nature"):
-			drain += heal_rate * minf(float(tile.ley_line_count), 3.0)
-
-		if incoming == 0.0 and tile.corruption_pressure == 0.0:
-			continue
-		tile.corruption_pressure = clampf(tile.corruption_pressure + incoming - drain, 0.0, 1.0)
-
-	# Terrain flip: pressure crosses threshold → corrupted_land
-	# Water tiles (ocean, lake, inland_sea, coast) never flip terrain — corruption
-	# in water expresses through the marine ecosystem (reef_health, fish_stock) instead.
-	for axial: Vector2i in game_map.tiles:
-		var tile: Variant = game_map.tiles[axial]
-		var tid: String = tile.terrain_id
-		if (
-			tid == "corrupted_land"
-			or tid == "ocean"
-			or tid == "lake"
-			or tid == "inland_sea"
-			or tid == "coast"
-		):
-			continue
-		if tile.corruption_pressure > flip_threshold:
-			if tile.original_terrain_id == "":
-				tile.original_terrain_id = tile.terrain_id
-			tile.terrain_id = "corrupted_land"
-			EventBus.corruption_spread.emit(tile)
-
-	# Marine corruption: coast tiles with elevated pressure degrade reef and fish stock
-	# (corrupted fish and algae carry corruption through the marine ecosystem)
-	for axial: Vector2i in game_map.tiles:
-		var tile: Variant = game_map.tiles[axial]
-		if tile.terrain_id != "coast":
-			continue
-		if tile.corruption_pressure > 0.2:
-			tile.reef_health = maxf(0.0, tile.reef_health - tile.corruption_pressure * 0.015)
-			if tile.fish_stock > 0:
-				tile.fish_stock = maxf(0.0, tile.fish_stock - tile.corruption_pressure * 0.01)
-
-	# Terrain healing: corrupted tile's pressure falls below heal threshold → restore
-	for axial: Vector2i in game_map.tiles:
-		var tile: Variant = game_map.tiles[axial]
-		if tile.terrain_id != "corrupted_land" or tile.corruption_pressure > heal_threshold:
-			continue
-		var original: String = tile.original_terrain_id
-		var restore_to: String = original if original != "" else "grassland"
-		tile.terrain_id = restore_to
-		tile.original_terrain_id = ""
-		EventBus.corruption_healed.emit(tile)
 
 
 # -- Internal helpers --
 
 
-func _get_terrain_data(terrain_id: String) -> Dictionary:
-	if not _terrain_cache.has(terrain_id):
-		_terrain_cache[terrain_id] = DataLoader.get_terrain(terrain_id)
-	return _terrain_cache[terrain_id]
+func _get_terrain_data(biome_id: String) -> Dictionary:
+	if not _terrain_cache.has(biome_id):
+		_terrain_cache[biome_id] = DataLoader.get_terrain(biome_id)
+	return _terrain_cache[biome_id]
 
 
 func _solar_by_latitude(row: int, center_row: float) -> float:
-	## Solar input at a given map row: 1.0 at equator (center), 0.0 at poles.
-	return 1.0 - absf((float(row) - center_row) / center_row)
+	## Solar input at a given map row, clamped to habitable range.
+	## Raw latitude factor: 1.0 at equator, 0.0 at poles.
+	## Mapped via solar_min/solar_max params to produce stable equilibrium
+	## temperatures that support reef survival and biome diversity.
+	var raw: float = 1.0 - absf((float(row) - center_row) / center_row)
+	var solar_min: float = _params.get("solar_min", _DEFAULTS.get("solar_min", 0.15))
+	var solar_max: float = _params.get("solar_max", _DEFAULTS.get("solar_max", 0.70))
+	return solar_min + (solar_max - solar_min) * raw
 
 
 func _upwind_pos(axial: Vector2i, wind_dir: int) -> Vector2i:
diff --git a/engine/src/modules/climate/climate_spec_eval.gd b/engine/src/modules/climate/climate_spec_eval.gd
index 0d28ad09..8cd64004 100644
--- a/engine/src/modules/climate/climate_spec_eval.gd
+++ b/engine/src/modules/climate/climate_spec_eval.gd
@@ -4,20 +4,21 @@ extends RefCounted
 ## Pure logic — no side effects, no state mutation. Used by Climate and the transpiler.
 
 const MapGeneratorScript: GDScript = preload("res://engine/src/generation/map_generator.gd")
+const BiomeClassifierScript = preload("res://engine/src/models/world/biome_classifier.gd")
 
 
 static func ideal_terrain(tile: Variant, spec: Dictionary) -> String:
 	## Determine the climate-ideal terrain type for a tile. Reads transition rules
 	## from climate_spec.json terrain_transitions. If a terrain has no spec entry,
-	## falls back to classify_terrain.
-	var tid: String = tile.terrain_id
+	## falls back to BiomeClassifier.classify().
+	var tid: String = tile.biome_id
 	var temp: float = tile.temperature
 	var moist: float = tile.moisture
 
 	var transitions: Dictionary = spec.get("terrain_transitions", {})
 	var rules: Array = transitions.get(tid, [])
 	if rules.is_empty():
-		return MapGeneratorScript.classify_terrain(temp, moist, tile.elevation)
+		return BiomeClassifierScript.classify(tile)
 
 	for rule: Variant in rules:
 		if not rule is Dictionary:
@@ -25,7 +26,7 @@ static func ideal_terrain(tile: Variant, spec: Dictionary) -> String:
 		if eval_condition(rule.get("condition", ""), temp, moist, tile.elevation):
 			var becomes: String = rule.get("becomes", "")
 			if becomes == "classify":
-				return MapGeneratorScript.classify_terrain(temp, moist, tile.elevation)
+				return BiomeClassifierScript.classify(tile)
 			return becomes
 
 	return tid
diff --git a/engine/src/modules/climate/ecological_event_handlers_a.gd b/engine/src/modules/climate/ecological_event_handlers_a.gd
index 56015be6..8db61a72 100644
--- a/engine/src/modules/climate/ecological_event_handlers_a.gd
+++ b/engine/src/modules/climate/ecological_event_handlers_a.gd
@@ -27,7 +27,7 @@ static func process_volcanic(
 	var center: Variant = EcoUtils.pick_land(game_map, w, h, turn_seed, channel)
 	if center == null or center.is_natural_wonder():
 		return
-	center.terrain_id = "volcano"
+	center.biome_id = "volcano"
 	center.quality = 1
 	center.quality_progress = 0
 
@@ -41,8 +41,8 @@ static func process_volcanic(
 		var t: Variant = game_map.tiles[axial]
 		if t == center or t.is_natural_wonder():
 			continue
-		if t.terrain_id != "ocean" and t.terrain_id != "coast":
-			t.terrain_id = scorched_terrain
+		if t.biome_id != "ocean" and t.biome_id != "coast":
+			t.biome_id = scorched_terrain
 			t.moisture = maxf(0.0, t.moisture - moisture_loss)
 			t.quality = 1
 			scorched += 1
@@ -105,13 +105,12 @@ static func process_impact(
 			var t: Variant = game_map.tiles[naxial]
 			if t.is_natural_wonder():
 				continue
-			if t.terrain_id != "ocean" and t.terrain_id != "coast":
-				t.terrain_id = "desert"
+			if t.biome_id != "ocean" and t.biome_id != "coast":
+				t.biome_id = "desert"
 				t.elevation = maxf(0.0, t.elevation - elev_loss)
 				t.moisture = 0.0
 				t.quality = 1
 				t.resource_id = ""
-				t.corruption_pressure = 1.0
 		# Phase 2: Global aerosol
 		for naxial: Vector2i in game_map.tiles:
 			game_map.tiles[naxial].sulfate_aerosol += aerosol_strength
@@ -120,18 +119,18 @@ static func process_impact(
 			var t: Variant = game_map.tiles[naxial]
 			if t.is_natural_wonder():
 				continue
-			if t.terrain_id in living_terrains:
+			if t.biome_id in living_terrains:
 				t.quality = maxi(1, t.quality - biome_kill_quality)
-				if t.terrain_id == "jungle":
-					t.terrain_id = "grassland"
+				if t.biome_id == "jungle":
+					t.biome_id = "grassland"
 					t.moisture = maxf(0.0, t.moisture - 0.15)
-				elif t.terrain_id == "enchanted_forest":
-					t.terrain_id = "forest"
-				elif t.terrain_id == "swamp":
-					t.terrain_id = "desert"
+				elif t.biome_id == "enchanted_forest":
+					t.biome_id = "forest"
+				elif t.biome_id == "swamp":
+					t.biome_id = "desert"
 					t.moisture = 0.0
 		# Phase 4: Impact site becomes mana node
-		center.terrain_id = "mana_node"
+		center.biome_id = "mana_node"
 		center.quality = 5
 		EcoUtils.set_wonder_anchor(center, tier_cfg, 5, ["death", "chaos"])
 		EcoUtils.spawn_resource(center, tier_cfg)
@@ -159,13 +158,13 @@ static func process_impact(
 	if elev_delta > 0.0:
 		# Raises terrain (e.g. mountain ridge)
 		var crater_terrain: String = tier_cfg.get("crater_terrain", "mountains")
-		center.terrain_id = crater_terrain
+		center.biome_id = crater_terrain
 		center.elevation = minf(1.0, center.elevation + elev_delta)
 		center.moisture = maxf(0.0, center.moisture - 0.1)
 		center.quality = 3
 	else:
 		# Depresses terrain (crater lake or barren)
-		center.terrain_id = "lake" if center.elevation < 0.15 else "desert"
+		center.biome_id = "lake" if center.elevation < 0.15 else "desert"
 		center.elevation = maxf(0.0, center.elevation + elev_delta)
 		center.quality = 1
 
@@ -194,7 +193,7 @@ static func process_impact(
 			var t: Variant = game_map.tiles[naxial]
 			if t.is_natural_wonder() or t.resource_id != "":
 				continue
-			if t.terrain_id == "ocean" or t.terrain_id == "coast":
+			if t.biome_id == "ocean" or t.biome_id == "coast":
 				continue
 			var tile_roll: float = EcoUtils.hash_noise(
 				float(scatter_idx), float(naxial.x + naxial.y), turn_seed + 7.0
@@ -282,7 +281,7 @@ static func process_wildfire(
 	var forest_types: Array = cat_cfg.get(
 		"target_terrain", ["forest", "jungle", "boreal_forest", "enchanted_forest"]
 	)
-	if not (center.terrain_id in forest_types):
+	if not (center.biome_id in forest_types):
 		return
 
 	var radius: int = tier_cfg.get("radius", 1)
@@ -296,9 +295,9 @@ static func process_wildfire(
 		var t: Variant = game_map.tiles[axial]
 		if t.is_natural_wonder():
 			continue
-		if t.terrain_id in forest_types:
+		if t.biome_id in forest_types:
 			if becomes != null and str(becomes) != "null":
-				t.terrain_id = str(becomes)
+				t.biome_id = str(becomes)
 			if quality_loss > 0:
 				t.quality = maxi(1, t.quality - quality_loss)
 				t.quality_progress = 0
@@ -343,7 +342,7 @@ static func process_drought(
 		if not game_map.tiles.has(axial):
 			continue
 		var t: Variant = game_map.tiles[axial]
-		if t.terrain_id != "ocean" and t.terrain_id != "coast":
+		if t.biome_id != "ocean" and t.biome_id != "coast":
 			t.moisture = maxf(0.0, t.moisture - moisture_loss)
 
 	var tier_name: String = tier_cfg.get("name", "Drought")
@@ -373,7 +372,7 @@ static func process_plague(
 	var target_terrain: Array = tier_cfg.get(
 		"target_terrain", ["grassland", "plains", "forest", "jungle", "enchanted_forest"]
 	)
-	if not (center.terrain_id in target_terrain):
+	if not (center.biome_id in target_terrain):
 		return
 
 	var radius: int = tier_cfg.get("radius", 2)
@@ -386,11 +385,11 @@ static func process_plague(
 		var t: Variant = game_map.tiles[axial]
 		if t.is_natural_wonder():
 			continue
-		if not (t.terrain_id in target_terrain):
+		if not (t.biome_id in target_terrain):
 			continue
 		t.quality = maxi(1, t.quality - quality_loss)
-		if terrain_downgrade.has(t.terrain_id):
-			t.terrain_id = str(terrain_downgrade[t.terrain_id])
+		if terrain_downgrade.has(t.biome_id):
+			t.biome_id = str(terrain_downgrade[t.biome_id])
 		affected += 1
 
 	if affected == 0:
diff --git a/engine/src/modules/climate/ecological_event_handlers_b.gd b/engine/src/modules/climate/ecological_event_handlers_b.gd
index a008b233..95f5a827 100644
--- a/engine/src/modules/climate/ecological_event_handlers_b.gd
+++ b/engine/src/modules/climate/ecological_event_handlers_b.gd
@@ -56,7 +56,7 @@ static func _apply_magical_positive(
 ) -> void:
 	var center_terrain: Variant = tier_cfg.get("center_terrain", null)
 	if center_terrain != null and str(center_terrain) != "null":
-		center.terrain_id = str(center_terrain)
+		center.biome_id = str(center_terrain)
 	var center_quality: int = tier_cfg.get("center_quality", 3)
 	center.quality = center_quality
 
@@ -70,13 +70,13 @@ static func _apply_magical_positive(
 			var t: Variant = game_map.tiles[axial]
 			if t == center or t.is_natural_wonder():
 				continue
-			if t.terrain_id == "ocean" or t.terrain_id == "coast":
+			if t.biome_id == "ocean" or t.biome_id == "coast":
 				continue
 			if moisture_gain > 0.0:
 				t.moisture = minf(1.0, t.moisture + moisture_gain)
 			if grassland_upgrade != null and str(grassland_upgrade) != "null":
-				if t.terrain_id == "grassland" or t.terrain_id == "plains":
-					t.terrain_id = str(grassland_upgrade)
+				if t.biome_id == "grassland" or t.biome_id == "plains":
+					t.biome_id = str(grassland_upgrade)
 
 	# Location-based school selection for wellspring
 	var schools: Array[String] = []
@@ -122,26 +122,22 @@ static func _apply_magical_negative(
 ) -> void:
 	var center_terrain: Variant = tier_cfg.get("center_terrain", null)
 	if center_terrain != null and str(center_terrain) != "null":
-		center.terrain_id = str(center_terrain)
+		center.biome_id = str(center_terrain)
 	var center_quality: int = tier_cfg.get("center_quality", 1)
 	center.quality = center_quality
 
 	var radius: int = tier_cfg.get("radius", 0)
-	var corruption_gain: float = tier_cfg.get("corruption_gain", 0.0)
 	var heat_delta: float = tier_cfg.get("heat_delta", 0.0)
-	if radius > 0:
+	if radius > 0 and heat_delta != 0.0:
 		for axial: Vector2i in EcoUtils.tiles_in_radius(center, radius):
 			if not game_map.tiles.has(axial):
 				continue
 			var t: Variant = game_map.tiles[axial]
 			if t == center or t.is_natural_wonder():
 				continue
-			if t.terrain_id == "ocean" or t.terrain_id == "coast":
+			if t.biome_id == "ocean" or t.biome_id == "coast":
 				continue
-			if corruption_gain > 0.0:
-				t.corruption_pressure = minf(1.0, t.corruption_pressure + corruption_gain)
-			if heat_delta != 0.0:
-				t.magic_heat_delta += heat_delta
+			t.magic_heat_delta += heat_delta
 
 	var raw_schools: Array = tier_cfg.get("anchor_schools", [])
 	var default_schools: Array = []
@@ -156,7 +152,7 @@ static func _apply_magical_negative(
 			turn,
 			event_type,
 			center,
-			"%s — T%d anchor, corruption spreads" % [tier_name, center.wonder_tier]
+			"%s — T%d anchor" % [tier_name, center.wonder_tier]
 		)
 	)
 
@@ -179,7 +175,7 @@ static func process_marine(
 	if not game_map.tiles.has(axial):
 		return
 	var center: Variant = game_map.tiles[axial]
-	if center.terrain_id != "coast" and center.terrain_id != "ocean":
+	if center.biome_id != "coast" and center.biome_id != "ocean":
 		return
 
 	var radius: int = tier_cfg.get("radius", 2)
@@ -192,19 +188,16 @@ static func process_marine(
 	var fish_stock_loss: int = tier_cfg.get("fish_stock_loss", 0)
 	var fish_stock_kill: bool = tier_cfg.get("fish_stock_kill", false)
 	var moisture_gain: float = tier_cfg.get("moisture_gain", 0.0)
-	var coast_corruption: float = tier_cfg.get("coast_corruption", 0.0)
 
 	for naxial: Vector2i in EcoUtils.tiles_in_radius(center, radius):
 		if not game_map.tiles.has(naxial):
 			continue
 		var t: Variant = game_map.tiles[naxial]
-		if t.terrain_id == "coast":
+		if t.biome_id == "coast":
 			if reef_health_gain > 0.0:
 				t.reef_health = minf(1.0, t.reef_health + reef_health_gain)
 			if reef_health_loss > 0.0:
 				t.reef_health = maxf(0.0, t.reef_health - reef_health_loss)
-			if coast_corruption > 0.0:
-				t.corruption_pressure = minf(1.0, t.corruption_pressure + coast_corruption)
 			if t.fish_stock >= 0:
 				if fish_stock_gain > 0:
 					t.fish_stock = mini(100, t.fish_stock + fish_stock_gain)
@@ -212,7 +205,7 @@ static func process_marine(
 					t.fish_stock = maxi(0, t.fish_stock - fish_stock_loss)
 				elif fish_stock_kill:
 					t.fish_stock = 0
-		elif t.terrain_id == "ocean":
+		elif t.biome_id == "ocean":
 			if moisture_gain > 0.0:
 				t.moisture = minf(1.0, t.moisture + moisture_gain)
 			if t.fish_stock >= 0:
@@ -222,7 +215,7 @@ static func process_marine(
 					t.fish_stock = maxi(0, t.fish_stock - fish_stock_loss)
 				elif fish_stock_kill:
 					t.fish_stock = 0
-		elif moisture_gain > 0.0 and t.terrain_id != "ocean":
+		elif moisture_gain > 0.0 and t.biome_id != "ocean":
 			t.moisture = minf(1.0, t.moisture + moisture_gain)
 
 	var polarity: String = "enriches" if positive else "harms"
@@ -295,7 +288,7 @@ static func process_glacial(
 			if warm_delta != 0.0:
 				t.magic_heat_delta += warm_delta
 				t.glacial_forcing += warm_delta
-			if moisture_surge > 0.0 and t.terrain_id == "coast":
+			if moisture_surge > 0.0 and t.biome_id == "coast":
 				t.moisture = minf(1.0, t.moisture + moisture_surge)
 		var coastal_reach: int = tier_cfg.get("coastal_flood_reach", 2)
 		events.append(
@@ -341,8 +334,8 @@ static func process_glacial(
 			for edge: int in t.river_edges:
 				if t.river_flow.has(edge):
 					t.river_flow[edge] = -abs(t.river_flow[edge])
-		if tundra_expansion and (t.terrain_id == "grassland" or t.terrain_id == "plains"):
-			t.terrain_id = "tundra"
+		if tundra_expansion and (t.biome_id == "grassland" or t.biome_id == "plains"):
+			t.biome_id = "tundra"
 		if quality_loss > 0:
 			t.quality = maxi(1, t.quality - quality_loss)
 		if moisture_loss > 0.0:
@@ -377,7 +370,7 @@ static func process_tsunami(
 	if not game_map.tiles.has(axial):
 		return
 	var coast_tile: Variant = game_map.tiles[axial]
-	if coast_tile.terrain_id != "coast":
+	if coast_tile.biome_id != "coast":
 		return
 
 	var inland_reach: int = tier_cfg.get("inland_reach", 1)
@@ -392,7 +385,7 @@ static func process_tsunami(
 		if not game_map.tiles.has(naxial):
 			continue
 		var t: Variant = game_map.tiles[naxial]
-		if t.terrain_id == "ocean" or t.terrain_id == "coast":
+		if t.biome_id == "ocean" or t.biome_id == "coast":
 			if reef_destruction:
 				t.reef_health = maxf(0.0, t.reef_health - 0.5)
 			continue
@@ -449,6 +442,11 @@ static func process_pandemic(
 				)
 				if lair_roll < lair_kill_chance:
 					t.lair_type = ""
+					# Convert NPC building to ruin
+					for b: Variant in GameState.get_npc_buildings_at(axial):
+						if b.type_id != "village" and b.type_id != "ruin":
+							b.type_id = "ruin"
+							b.name = "Ruin"
 					killed_lairs += 1
 			if fish_stock_loss > 0 and t.fish_stock >= 0:
 				t.fish_stock = maxi(0, t.fish_stock - fish_stock_loss)
diff --git a/engine/src/modules/climate/ecological_event_utils.gd b/engine/src/modules/climate/ecological_event_utils.gd
index 08f1add3..e0a57a4d 100644
--- a/engine/src/modules/climate/ecological_event_utils.gd
+++ b/engine/src/modules/climate/ecological_event_utils.gd
@@ -53,7 +53,7 @@ static func pick_land(
 	if not game_map.tiles.has(axial):
 		return null
 	var tile: Variant = game_map.tiles[axial]
-	if tile.terrain_id == "ocean" or tile.terrain_id == "coast":
+	if tile.biome_id == "ocean" or tile.biome_id == "coast":
 		return null
 	return tile
 
@@ -68,7 +68,7 @@ static func spawn_resource(tile: Variant, cfg: Dictionary) -> void:
 	## Handles two config shapes:
 	##   spawns_resource + resource_terrain  → always spawn that resource
 	##   resource_table [{ resource, weight, resource_terrain }]  → weighted random pick
-	## resource_terrain: if non-null, the tile's terrain_id is set to that value first.
+	## resource_terrain: if non-null, the tile's biome_id is set to that value first.
 	var table: Array = cfg.get("resource_table", [])
 	if not table.is_empty():
 		spawn_resource_weighted(tile, table)
@@ -79,7 +79,7 @@ static func spawn_resource(tile: Variant, cfg: Dictionary) -> void:
 		return
 	var resource_terrain: Variant = cfg.get("resource_terrain", null)
 	if resource_terrain != null and str(resource_terrain) != "null":
-		tile.terrain_id = str(resource_terrain)
+		tile.biome_id = str(resource_terrain)
 	tile.resource_id = resource_id
 
 
@@ -102,7 +102,7 @@ static func spawn_resource_weighted(tile: Variant, table: Array) -> void:
 			var resource_id: String = str(entry.get("resource", ""))
 			var resource_terrain: Variant = entry.get("resource_terrain", null)
 			if resource_terrain != null and str(resource_terrain) != "null":
-				tile.terrain_id = str(resource_terrain)
+				tile.biome_id = str(resource_terrain)
 			if resource_id != "":
 				tile.resource_id = resource_id
 			return