Initial scaffold: Godot 4.3 scenes, systems, and placeholders.

Wire all twelve levels with billboard prefabs, autoload systems (inventory, achievements, mock shop, DE/EN/BY), and satire audio locks so the Title→End flow is playable with placeholder assets.

scripts/combat/exit_trigger.gd

@@ -0,0 +1,25 @@
+extends Area3D
+class_name ExitTrigger
+## Walk into this volume to advance or jump to a scene.
+
+@export var next_scene_id: String = ""
+@export var use_goto_next: bool = true
+@export var require_flag: String = ""
+
+func _ready() -> void:
+	body_entered.connect(_on_body_entered)
+	collision_layer = 0
+	collision_mask = 2 # player layer
+
+func _on_body_entered(body: Node3D) -> void:
+	if not body.is_in_group("player"):
+		return
+	if require_flag != "" and not GameState.get_flag(require_flag, false):
+		var ui := get_node_or_null("/root/UIRoot")
+		if ui and ui.has_method("show_dialog"):
+			ui.show_dialog(Locale.tr_key("exit_hint") + " (?)")
+		return
+	if use_goto_next and next_scene_id == "":
+		GameState.goto_next()
+	elif next_scene_id != "":
+		GameState.goto_scene(next_scene_id)

scripts/combat/hazard_zone.gd

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+extends Area3D
+class_name HazardZone
+## Damages the player on enter.
+
+@export var damage: int = 1
+@export var death_cause_key: String = "death_default"
+@export var cooldown: float = 1.0
+
+var _ready_to_hurt: bool = true
+
+func _ready() -> void:
+	body_entered.connect(_on_body_entered)
+	collision_layer = 0
+	collision_mask = 2
+
+func _on_body_entered(body: Node3D) -> void:
+	if not _ready_to_hurt:
+		return
+	if not body.is_in_group("player"):
+		return
+	_ready_to_hurt = false
+	GameState.take_damage(damage, death_cause_key)
+	await get_tree().create_timer(cooldown).timeout
+	_ready_to_hurt = true

scripts/combat/hittable.gd

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+extends Node3D
+class_name HittableEntity
+## Generic enemy / boss stub with hit points.
+
+signal defeated
+signal hit(remaining_hp: int)
+
+@export var max_hp: int = 4
+@export var texture_path: String = "res://assets/sprites/placeholders/enemy.png"
+@export var defeat_flag: String = ""
+@export var achievement_on_defeat: String = ""
+
+var hp: int = 4
+var _alive: bool = true
+
+@onready var _billboard: BillboardSprite = $BillboardSprite
+
+func _ready() -> void:
+	hp = max_hp
+	add_to_group("enemy")
+	add_to_group("interactable")
+	if _billboard:
+		var tex: Texture2D = load(texture_path)
+		if tex:
+			_billboard.set_texture(tex)
+
+func take_hit(amount: int = 1) -> void:
+	if not _alive:
+		return
+	hp = max(0, hp - amount)
+	hit.emit(hp)
+	AudioDirector.play_hit()
+	if hp <= 0:
+		_alive = false
+		if defeat_flag != "":
+			GameState.set_flag(defeat_flag, true)
+		if achievement_on_defeat != "":
+			Achievements.unlock(achievement_on_defeat)
+		defeated.emit()
+		queue_free()
+
+func on_interact(_player: Node) -> void:
+	take_hit(1)

scripts/combat/interactable_npc.gd

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+extends Node3D
+class_name InteractableNPC
+## Billboard NPC with dialog key and optional quest hook.
+
+signal interacted(npc: InteractableNPC)
+
+@export var dialog_key: String = "dialog_hongkong_npc"
+@export var texture_path: String = "res://assets/sprites/placeholders/npc.png"
+@export var give_item_id: String = ""
+@export var require_item_id: String = ""
+@export var consume_required: bool = false
+@export var quest_flag: String = ""
+@export var achievement_id: String = ""
+@export var on_success_goto: String = ""
+
+@onready var _billboard: BillboardSprite = $BillboardSprite
+
+func _ready() -> void:
+	add_to_group("interactable")
+	if _billboard:
+		var tex: Texture2D = load(texture_path)
+		if tex:
+			_billboard.set_texture(tex)
+
+func on_interact(_player: Node) -> void:
+	interacted.emit(self)
+	var ui := get_node_or_null("/root/UIRoot")
+	if ui and ui.has_method("show_dialog"):
+		ui.show_dialog(Locale.tr_key(dialog_key))
+	if require_item_id != "" and not Inventory.has_item(require_item_id):
+		return
+	if require_item_id != "" and consume_required:
+		Inventory.remove_item(require_item_id, 1)
+	if give_item_id != "":
+		Inventory.add_item(give_item_id, 1)
+	if quest_flag != "":
+		GameState.set_flag(quest_flag, true)
+		if quest_flag == "house_built":
+			GameState.house_built = true
+	if achievement_id != "":
+		Achievements.unlock(achievement_id)
+	if on_success_goto != "":
+		GameState.goto_scene(on_success_goto)