Progress persistence

levels/mechanic_test/prop_test.tscn

@@ -1,6 +1,7 @@
-[gd_scene load_steps=12 format=4 uid="uid://cfqirm2o3uo4k"]
+[gd_scene load_steps=13 format=4 uid="uid://cfqirm2o3uo4k"]
 
 [ext_resource type="PackedScene" uid="uid://c2omlx4ptrc01" path="res://src/world/gunk_body/gunk_body.tscn" id="1_cr8wn"]
+[ext_resource type="Texture2D" uid="uid://8cm835h4gxwe" path="res://assets/debug_mask.png" id="2_7477u"]
 [ext_resource type="Shader" uid="uid://ckxc0ngd37rtk" path="res://src/shaders/gunk.gdshader" id="2_lrgpr"]
 [ext_resource type="FastNoiseLite" uid="uid://cnlvdtx68giv6" path="res://assets/materials/gunk_noise.tres" id="3_7477u"]
 
@@ -57,7 +58,7 @@ seamless = true
 seamless_blend_skirt = 0.5
 noise = ExtResource("3_7477u")
 
-[sub_resource type="ShaderMaterial" id="ShaderMaterial_qjnj2"]
+[sub_resource type="ShaderMaterial" id="ShaderMaterial_lrgpr"]
 resource_local_to_scene = true
 render_priority = 0
 shader = ExtResource("2_lrgpr")
@@ -69,6 +70,7 @@ shader_parameter/time_pixellation = 30.0
 shader_parameter/roughness = 0.15
 shader_parameter/specular_contribution = 0.8
 shader_parameter/emission_strength = 0.02
+shader_parameter/normal_scale = 1.0
 shader_parameter/uv_scale = Vector2(4, 4)
 shader_parameter/time_scale = 0.2
 shader_parameter/edge_bleed = 0.25
@@ -79,6 +81,7 @@ shader_parameter/jitter_magnitude = 0.0
 shader_parameter/jitter_time_scale = 0.1
 shader_parameter/vertex_inflation = 0.0
 shader_parameter/inflation_pixellation = 10.0
+shader_parameter/overlay_emission_scale = 1.0
 
 [sub_resource type="ConcavePolygonShape3D" id="ConcavePolygonShape3D_x2vho"]
 data = PackedVector3Array(-1, 1, 0.1, -1, -0.8, 0.1, -1, 1, -0.1, -1, 1, -0.1, -1, -0.8, 0.1, -1, -0.8, -0.1, -1, -1, 0.1, -1, -0.8, -0.1, -1, -0.8, 0.1, -1, -1, -2.3, -1, -0.8, -0.1, -1, -1, 0.1, -1, -0.8, -2.3, -1, -0.8, -0.1, -1, -1, -2.3, -1, -0.8, -2.1, -1, -0.8, -0.1, -1, -0.8, -2.3, -1, -0.8, -2.1, -1, -0.8, -2.3, -1, 1, -2.1, -1, 1, -2.1, -1, -0.8, -2.3, -1, 1, -2.3, -1, 1, -0.1, -1, -0.8, -0.1, 1, 1, -0.1, 1, 1, -0.1, -1, -0.8, -0.1, 1, -0.8, -0.1, 1, 1, -0.1, 1, -0.8, -0.1, 1, 1, 0.1, 1, 1, 0.1, 1, -0.8, -0.1, 1, -0.8, 0.1, 1, -0.8, -0.1, 1, -1, 0.1, 1, -0.8, 0.1, 1, -0.8, -2.1, 1, -1, 0.1, 1, -0.8, -0.1, 1, -0.8, -2.3, 1, -1, 0.1, 1, -0.8, -2.1, 1, -1, -2.3, 1, -1, 0.1, 1, -0.8, -2.3, 1, -0.8, -2.3, 1, -0.8, -2.1, 1, 1, -2.3, 1, 1, -2.3, 1, -0.8, -2.1, 1, 1, -2.1, 1, 1, 0.1, 1, -0.8, 0.1, -1, 1, 0.1, -1, 1, 0.1, 1, -0.8, 0.1, -1, -0.8, 0.1, 1, -0.8, 0.1, 1, -1, 0.1, -1, -0.8, 0.1, -1, -0.8, 0.1, 1, -1, 0.1, -1, -1, 0.1, -1, -1, -2.3, -1, -1, 0.1, 1, -1, -2.3, 1, -1, -2.3, -1, -1, 0.1, 1, -1, 0.1, -1, 1, -0.1, 1, 1, -0.1, -1, 1, 0.1, -1, 1, 0.1, 1, 1, -0.1, 1, 1, 0.1, 1, -0.8, -0.1, -1, -0.8, -0.1, 1, -0.8, -2.1, 1, -0.8, -2.1, -1, -0.8, -0.1, -1, -0.8, -2.1, -1, -0.8, -2.3, -1, -1, -2.3, 1, -0.8, -2.3, 1, -0.8, -2.3, -1, -1, -2.3, 1, -1, -2.3, -1, -0.8, -2.3, 1, -0.8, -2.3, -1, 1, -2.3, -1, 1, -2.3, 1, -0.8, -2.3, 1, 1, -2.3, 1, 1, -2.1, -1, 1, -2.1, 1, 1, -2.3, 1, 1, -2.3, -1, 1, -2.1, -1, 1, -2.3, 1, -0.8, -2.1, -1, -0.8, -2.1, 1, 1, -2.1, 1, 1, -2.1, -1, -0.8, -2.1, -1, 1, -2.1)
@@ -92,7 +95,8 @@ skeleton = NodePath("GunkBody")
 
 [node name="GunkBody" parent="Parallel" instance=ExtResource("1_cr8wn")]
 mask_dim = 128
-source_gunk_material = SubResource("ShaderMaterial_qjnj2")
+initial_mask = ExtResource("2_7477u")
+source_gunk_material = SubResource("ShaderMaterial_lrgpr")
 
 [node name="CollisionShape3D" type="CollisionShape3D" parent="Parallel/GunkBody"]
 shape = SubResource("ConcavePolygonShape3D_x2vho")

project.godot

@@ -88,6 +88,7 @@ MeetSpookSource="meet-spook event sources"
 LurkPoint="Point which a lurking beast may wander to."
 BeastSpawnPoint="Spawn point for a grunkbeast"
 GrunkBeast="GrunkBeast instances."
+Persistent="Nodes which implement save and load methods"
 
 [importer_defaults]
 

src/game/game.tscn

@@ -10,46 +10,6 @@ Label/constants/outline_size = 16
 Label/font_sizes/font_size = 32
 Label/fonts/font = ExtResource("2_s6lek")
 
-[sub_resource type="Animation" id="Animation_s6lek"]
-resource_name = "initial_display"
-step = 0.05
-tracks/0/type = "value"
-tracks/0/imported = false
-tracks/0/enabled = true
-tracks/0/path = NodePath("MarginContainer/HBoxContainer/Loading:visible_ratio")
-tracks/0/interp = 1
-tracks/0/loop_wrap = true
-tracks/0/keys = {
-"times": PackedFloat32Array(0, 0.8, 1),
-"transitions": PackedFloat32Array(1, 1, 1),
-"update": 0,
-"values": [0.0, 0.0, 1.0]
-}
-tracks/1/type = "value"
-tracks/1/imported = false
-tracks/1/enabled = true
-tracks/1/path = NodePath("MarginContainer/HBoxContainer/Ellipsis:visible_characters")
-tracks/1/interp = 1
-tracks/1/loop_wrap = true
-tracks/1/keys = {
-"times": PackedFloat32Array(0),
-"transitions": PackedFloat32Array(1),
-"update": 1,
-"values": [0]
-}
-tracks/2/type = "value"
-tracks/2/imported = false
-tracks/2/enabled = true
-tracks/2/path = NodePath("MarginContainer/HBoxContainer/Blinker:visible")
-tracks/2/interp = 1
-tracks/2/loop_wrap = true
-tracks/2/keys = {
-"times": PackedFloat32Array(0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8),
-"transitions": PackedFloat32Array(1, 1, 1, 1, 1, 1, 1, 1, 1),
-"update": 1,
-"values": [false, true, false, true, false, true, false, true, false]
-}
-
 [sub_resource type="Animation" id="Animation_kgj8g"]
 length = 0.001
 tracks/0/type = "value"
@@ -131,6 +91,46 @@ tracks/2/keys = {
 "values": [0, 1, 2, 3]
 }
 
+[sub_resource type="Animation" id="Animation_s6lek"]
+resource_name = "initial_display"
+step = 0.05
+tracks/0/type = "value"
+tracks/0/imported = false
+tracks/0/enabled = true
+tracks/0/path = NodePath("MarginContainer/HBoxContainer/Loading:visible_ratio")
+tracks/0/interp = 1
+tracks/0/loop_wrap = true
+tracks/0/keys = {
+"times": PackedFloat32Array(0, 0.8, 1),
+"transitions": PackedFloat32Array(1, 1, 1),
+"update": 0,
+"values": [0.0, 0.0, 1.0]
+}
+tracks/1/type = "value"
+tracks/1/imported = false
+tracks/1/enabled = true
+tracks/1/path = NodePath("MarginContainer/HBoxContainer/Ellipsis:visible_characters")
+tracks/1/interp = 1
+tracks/1/loop_wrap = true
+tracks/1/keys = {
+"times": PackedFloat32Array(0),
+"transitions": PackedFloat32Array(1),
+"update": 1,
+"values": [0]
+}
+tracks/2/type = "value"
+tracks/2/imported = false
+tracks/2/enabled = true
+tracks/2/path = NodePath("MarginContainer/HBoxContainer/Blinker:visible")
+tracks/2/interp = 1
+tracks/2/loop_wrap = true
+tracks/2/keys = {
+"times": PackedFloat32Array(0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8),
+"transitions": PackedFloat32Array(1, 1, 1, 1, 1, 1, 1, 1, 1),
+"update": 1,
+"values": [false, true, false, true, false, true, false, true, false]
+}
+
 [sub_resource type="AnimationLibrary" id="AnimationLibrary_kgj8g"]
 _data = {
 &"RESET": SubResource("Animation_kgj8g"),

src/player/player.gd

@@ -264,4 +264,18 @@ func _physics_process(delta: float) -> void:
 
 	move_and_slide()
 
+
+#endregion
+
+
+#region Persistence
+func serialize() -> Dictionary:
+	return {
+		"inventory": inventory,
+	}
+
+
+func deserialize(data: Dictionary) -> void:
+	@warning_ignore("unsafe_cast")
+	inventory.assign(data["inventory"] as Dictionary)
 #endregion

src/player/player.tscn

@@ -592,7 +592,7 @@ _data = {
 
 [sub_resource type="PlaneMesh" id="PlaneMesh_p6grl"]
 
-[node name="Player" type="CharacterBody3D"]
+[node name="Player" type="CharacterBody3D" groups=["Persistent"]]
 collision_layer = 8
 collision_mask = 33
 script = ExtResource("1_npueo")

src/props/bulkhead/bulkhead.gd

@@ -1,5 +1,8 @@
 extends Node3D
 
+@export var start_open := false
+
+@export_category("Editor Tools")
 @export var debug_open: bool:
 	set(value):
 		open()
@@ -15,6 +18,28 @@ extends Node3D
 @onready var nav_link: NavigationLink3D = %NavLink
 
 
+func _ready() -> void:
+	if start_open:
+		_instant_open()
+
+
+func _instant_open() -> void:
+	nav_link.enabled = true
+	animation.play("open")
+	animation.advance(100)
+
+
+func _instant_close() -> void:
+	nav_link.enabled = false
+	animation.play("open")
+	animation.advance(0)
+	animation.stop()
+
+
+func is_open() -> bool:
+	return nav_link.enabled
+
+
 func open() -> void:
 	nav_link.enabled = true
 	animation.play("open")
@@ -27,3 +52,14 @@ func close() -> void:
 	# TODO bespoke close anim?
 	animation.play_backwards("open")
 	nav_link.enabled = false
+
+
+func serialize() -> Dictionary:
+	return {"open": is_open()}
+
+
+func deserialize(state: Dictionary) -> void:
+	if state["open"]:
+		_instant_open()
+	else:
+		_instant_close()  # unneccessary?

src/props/bulkhead/bulkhead.tscn

@@ -281,7 +281,7 @@ _data = {
 &"spray": SubResource("Animation_88qrs")
 }
 
-[node name="Bulkhead" instance=ExtResource("1_77udb")]
+[node name="Bulkhead" groups=["Persistent"] instance=ExtResource("1_77udb")]
 script = ExtResource("2_hknvo")
 
 [node name="Frame" parent="." index="0"]

src/props/retinal_scanner/retinal_scanner.gd

@@ -40,3 +40,12 @@ func _activate() -> void:
 func _on_interactive_selected() -> void:
 	if enabled:
 		interactive.enabled = _has_item()
+
+
+func serialize() -> Dictionary:
+	return {"enabled": enabled}
+
+
+func deserialize(state: Dictionary) -> void:
+	if state["enabled"]:
+		enable()

src/props/retinal_scanner/retinal_scanner.tscn

@@ -9,7 +9,7 @@ size = Vector3(0.475, 0.65, 0.2)
 [sub_resource type="BoxShape3D" id="BoxShape3D_5bfyo"]
 size = Vector3(0.475, 0.65, 0.2)
 
-[node name="RetinalScanner" type="Node3D"]
+[node name="RetinalScanner" type="Node3D" groups=["Persistent"]]
 script = ExtResource("1_c71b5")
 
 [node name="MeshInstance3D" type="MeshInstance3D" parent="."]

src/props/wall_switch/wall_switch.gd

@@ -85,3 +85,14 @@ func _on_gunk_body_clear_total_updated(clear_total: float) -> void:
 
 func _on_action_delay_timeout() -> void:
 	activated.emit()
+
+
+func serialize() -> Dictionary:
+	return {"enabled": enabled}
+
+
+func deserialize(state: Dictionary) -> void:
+	if state["enabled"]:
+		enable()
+	else:
+		disable()

src/props/wall_switch/wall_switch.tscn

@@ -189,7 +189,7 @@ size = Vector3(0.475, 0.65, 0.2)
 [sub_resource type="SphereShape3D" id="SphereShape3D_mxsyy"]
 radius = 3.0
 
-[node name="WallSwitch" instance=ExtResource("2_whafo")]
+[node name="WallSwitch" groups=["Persistent"] instance=ExtResource("2_whafo")]
 script = ExtResource("2_kfvqd")
 enabled = true
 label = "INTERACTIVE_SWITCH_LABEL"

src/world/gunk_body/gunk_body.gd

@@ -61,8 +61,7 @@ func _ready() -> void:
 	# Overlay mesh with gunk material
 	mesh_instance.material_overlay = mat_instance
 
-	if initial_mask:
+	_deferred_init.call_deferred()
-		mask_texture.texture = initial_mask
 
 	# Initialize meshtool
 	meshtool.create_from_surface(mesh_instance.mesh as ArrayMesh, 0)
@@ -71,6 +70,12 @@ func _ready() -> void:
 	_thread.start(_async_compute_clear_total)
 
 
+func _deferred_init() -> void:
+	if initial_mask:
+		mask_texture.texture = initial_mask
+		mask_texture.visible = true
+
+
 func _trigger_recompute_deferred() -> void:
 	_mutex.lock()
 	_mask_tx = mask_viewport.get_texture()
@@ -286,3 +291,13 @@ func _process(_delta: float) -> void:
 func _on_mask_painted() -> void:
 	# XXX any problem with posting each frame?
 	_trigger_recompute_deferred.call_deferred()
+
+
+func serialize() -> Dictionary:
+	var state := {"mask": mask_viewport.get_texture().get_image()}
+	return state
+
+
+func deserialize(state: Dictionary) -> void:
+	@warning_ignore("unsafe_cast")
+	initial_mask = ImageTexture.create_from_image(state["mask"] as Image)

src/world/gunk_body/gunk_body.tscn

@@ -5,7 +5,7 @@
 [ext_resource type="Script" uid="uid://bom5qysgfvap1" path="res://src/world/gunk_body/draw_controller.gd" id="2_kkcjw"]
 [ext_resource type="Script" uid="uid://ba7480ara8eo" path="res://levels/sandbox/debug_draw.gd" id="3_m8wx4"]
 
-[node name="GunkBody" type="StaticBody3D"]
+[node name="GunkBody" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 5
 collision_mask = 0
 script = ExtResource("1_qqbpr")

src/world/gunk_node/grunk_nodule.tscn

@@ -19,7 +19,7 @@ stream_1/stream = ExtResource("5_omayi")
 stream_2/stream = ExtResource("6_yg8lg")
 stream_3/stream = ExtResource("7_4kci5")
 
-[node name="GrunkNodule" type="StaticBody3D"]
+[node name="GrunkNodule" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 36
 collision_mask = 0
 script = ExtResource("1_iyr82")

src/world/gunk_node/gunk_node.gd

@@ -20,6 +20,10 @@ var _sustained_damage := 0.0
 var _hit_this_frame := false
 
 
+func _enter_tree() -> void:
+	add_to_group("Persistent", true)
+
+
 ## Called each frame this node takes a hit.
 ##
 ## Derived types should override `_hit()` as a lifecycle method.
@@ -68,3 +72,13 @@ func destroy() -> void:
 
 func _destroy() -> void:
 	pass  # Implemented in derived type
+
+
+func serialize() -> Dictionary:
+	# Nothing to serialize, but we need a placeholder value to show we haven't been destroyed.
+	return {}
+
+
+func deserialize(_state: Dictionary) -> void:
+	# Nothing to deserialize, but we won't be freed!
+	pass

src/world/mechanics/alarm/gunk_alarm.tscn

@@ -243,7 +243,7 @@ _data = {
 &"pulse": SubResource("Animation_vokcn")
 }
 
-[node name="GunkAlarm" type="StaticBody3D"]
+[node name="GunkAlarm" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 36
 collision_mask = 0
 script = ExtResource("1_piaxx")

src/world/mechanics/heart/gunk_heart.tscn

@@ -99,7 +99,7 @@ _data = {
 &"pulse": SubResource("Animation_eu6st")
 }
 
-[node name="GunkHeart" type="StaticBody3D"]
+[node name="GunkHeart" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 36
 collision_mask = 0
 script = ExtResource("1_ftym0")

src/world/mechanics/listener/listener.tscn

@@ -53,7 +53,7 @@ _data = {
 &"trigger": SubResource("Animation_htscg")
 }
 
-[node name="Listener" type="StaticBody3D"]
+[node name="Listener" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 36
 collision_mask = 0
 script = ExtResource("1_htscg")

src/world/mechanics/relay/gunk_relay.tscn

@@ -111,7 +111,7 @@ _data = {
 &"trigger": SubResource("Animation_rdv5j")
 }
 
-[node name="GunkRelay" type="StaticBody3D"]
+[node name="GunkRelay" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 36
 collision_mask = 0
 script = ExtResource("1_rdv5j")

src/world/mechanics/trigger/gunk_trigger.tscn

@@ -13,7 +13,7 @@ emission_energy_multiplier = 0.0
 [sub_resource type="ConcavePolygonShape3D" id="ConcavePolygonShape3D_t1c4j"]
 data = PackedVector3Array(0.7236, -0.4472, 0.5257, 0, -1, 0, -0.2764, -0.4472, 0.8506, 0, -1, 0, 0.7236, -0.4472, 0.5257, 0.7236, -0.4472, -0.5257, -0.2764, -0.4472, 0.8506, 0, -1, 0, -0.8944, -0.4472, 0, -0.8944, -0.4472, 0, 0, -1, 0, -0.2764, -0.4472, -0.8506, -0.2764, -0.4472, -0.8506, 0, -1, 0, 0.7236, -0.4472, -0.5257, 0.7236, -0.4472, -0.5257, 0.7236, -0.4472, 0.5257, 0.8944, 0.4472, 0, 0.7236, -0.4472, 0.5257, -0.2764, -0.4472, 0.8506, 0.2764, 0.4472, 0.8506, -0.2764, -0.4472, 0.8506, -0.8944, -0.4472, 0, -0.7236, 0.4472, 0.5257, -0.8944, -0.4472, 0, -0.2764, -0.4472, -0.8506, -0.7236, 0.4472, -0.5257, -0.2764, -0.4472, -0.8506, 0.7236, -0.4472, -0.5257, 0.2764, 0.4472, -0.8506, 0.8944, 0.4472, 0, 0.7236, -0.4472, 0.5257, 0.2764, 0.4472, 0.8506, 0.2764, 0.4472, 0.8506, -0.2764, -0.4472, 0.8506, -0.7236, 0.4472, 0.5257, -0.7236, 0.4472, 0.5257, -0.8944, -0.4472, 0, -0.7236, 0.4472, -0.5257, -0.7236, 0.4472, -0.5257, -0.2764, -0.4472, -0.8506, 0.2764, 0.4472, -0.8506, 0.2764, 0.4472, -0.8506, 0.7236, -0.4472, -0.5257, 0.8944, 0.4472, 0, 0.8944, 0.4472, 0, 0.2764, 0.4472, 0.8506, 0, 1, 0, 0.2764, 0.4472, 0.8506, -0.7236, 0.4472, 0.5257, 0, 1, 0, -0.7236, 0.4472, 0.5257, -0.7236, 0.4472, -0.5257, 0, 1, 0, -0.7236, 0.4472, -0.5257, 0.2764, 0.4472, -0.8506, 0, 1, 0, 0.2764, 0.4472, -0.8506, 0.8944, 0.4472, 0, 0, 1, 0)
 
-[node name="GunkTrigger" type="StaticBody3D"]
+[node name="GunkTrigger" type="StaticBody3D" groups=["Persistent"]]
 collision_layer = 36
 collision_mask = 0
 script = ExtResource("1_t1c4j")

src/world/save_state.gd

@@ -0,0 +1,81 @@
+class_name SaveState extends Resource
+## Serializable container for gameplay state.
+
+const CURRENT_VERSION := 0
+const PERSISTENT_GROUP := "Persistent"
+const SERIALIZE_METHOD := "serialize"
+const DESERIALIZE_METHOD := "deserialize"
+
+@export var save_version := CURRENT_VERSION
+
+@export var level_path: String
+
+@export var persistent_state: Dictionary[String, Dictionary] = {}
+
+@export_group("WorldManager State")
+@export var grunk_tank_limit: int
+@export var mp3_player_unlocked: bool
+@export var toothbrush_unlocked: bool
+@export var stickers_unlocked: bool
+
+@export var grunk_tank: float
+@export var grunk_vault: float
+@export var alert_level: int
+
+
+static func node_key(node: Node, world: World) -> String:
+	return str(world.level_root.get_path_to(node))
+
+
+func load_to_world(world: World) -> void:
+	if level_path != world.current_level.resource_path:
+		push_warning(
+			"This save is for ",
+			level_path,
+			" but the loaded level is for ",
+			world.current_level.resource_path
+		)
+
+	world.manager.grunk_tank_limit = grunk_tank_limit
+	world.manager.mp3_player_unlocked = mp3_player_unlocked
+	world.manager.toothbrush_unlocked = toothbrush_unlocked
+	world.manager.stickers_unlocked = stickers_unlocked
+	world.manager.grunk_tank = grunk_tank
+	world.manager.grunk_vault = grunk_vault
+	world.manager.alert_level = alert_level
+
+	var persistent := world.get_tree().get_nodes_in_group(PERSISTENT_GROUP)
+
+	for node: Node in persistent:
+		var key := SaveState.node_key(node, world)
+		if key in persistent_state:
+			# Node is in our persistent state, so load it with data.
+			Callable(node, DESERIALIZE_METHOD).call(persistent_state[key])
+		else:
+			# Node isn't in our persistent state, so it must have been destroyed.
+			node.queue_free()
+
+
+static func serialize(world: World) -> SaveState:
+	var save := SaveState.new()
+
+	save.level_path = world.current_level.resource_path
+
+	save.grunk_tank_limit = world.manager.grunk_tank_limit
+	save.mp3_player_unlocked = world.manager.mp3_player_unlocked
+	save.toothbrush_unlocked = world.manager.toothbrush_unlocked
+	save.stickers_unlocked = world.manager.stickers_unlocked
+	save.grunk_tank = world.manager.grunk_tank
+	save.grunk_vault = world.manager.grunk_vault
+	save.alert_level = world.manager.alert_level
+
+	# NOTE: I'm assuming that `persistent` will have the same order ever time the world is loaded.
+	# This may not be the case. If so, we need to find a different way to uniquely identify nodes.
+	var persistent := world.get_tree().get_nodes_in_group(PERSISTENT_GROUP)
+
+	for node: Node in persistent:
+		var key := SaveState.node_key(node, world)
+		var data: Dictionary = Callable(node, SERIALIZE_METHOD).call()
+		save.persistent_state[key] = data
+
+	return save

src/world/save_state.gd.uid

@@ -0,0 +1 @@
+uid://dsyyk7muaabf5

src/world/spook_manager/spook_manager.gd

@@ -51,8 +51,11 @@ func on_alert_raised(new_level: int) -> void:
 			# Set up meet-spook.
 			# Get closest MeetSpook point to player.
 			if Player.instance:
-				var closest := SceneTools.closest_in_group(Player.instance, MeetSpook.GROUP)
+				var closest := (
-				(closest as MeetSpook).prepare()
+					SceneTools.closest_in_group(Player.instance, MeetSpook.GROUP) as MeetSpook
+				)
+				if closest:
+					closest.prepare()
 		2:
 			# LEVEL 2: AGGRESSIVE
 			# Beast pursues player on sight.

src/world/world.gd

@@ -2,7 +2,7 @@ class_name World extends Node
 ## Access and flow control for the game world.
 
 @export var pause_enabled := true
-@export var save_path := "user://saved_game.tscn"
+@export var save_path := "user://save_state.res"
 
 @export var manager: WorldManager
 @export var spook_manager: SpookManager
@@ -46,11 +46,19 @@ func unpause() -> void:
 	get_tree().paused = false
 
 
-func load_level(level: PackedScene) -> void:
+func load_level(level: PackedScene, save: SaveState = null) -> void:
 	for c: Node in level_root.get_children():
 		c.queue_free()
+		level_root.remove_child(c)
 	current_level = level
-	level_root.add_child(level.instantiate())
+	print("Instantiating level from ", level.resource_path)
+	var level_instance := level.instantiate()
+	#if save:
+	#level_instance.ready.connect(func() -> void: save.load_to_world(self), CONNECT_ONE_SHOT)
+	level_root.add_child(level_instance)
+	if save:
+		save.load_to_world(self)
+	print("Done!")
 
 
 func on_player_death() -> void:
@@ -59,23 +67,21 @@ func on_player_death() -> void:
 	ui_root.add_child(kill_screen)
 
 
+func _reload_saved(save: SaveState) -> void:
+	load_level(current_level, save)
+
+
 func on_game_over() -> void:
-	# TODO: reload from last checkpoint
+	# reload the level from the last save
-	# in the mean time, just reload the level
+	if ResourceLoader.exists(save_path):
-	Game.instance.queue_scene(save_path)
+		Game.instance.queue_load(save_path).finally(_reload_saved)
-
+	else:
-
+		load_level(current_level)
-func _reown_tree(node: Node) -> void:
-	for c: Node in node.get_children():
-		c.set_owner(self)
-		_reown_tree(c)
 
 
 func save_progress() -> void:
-	# No way this works, right?
+	print("Preparing save state...")
-	print("Preparing world for save...")
+	var save := SaveState.serialize(self)
-	var save := PackedScene.new()
-	_reown_tree(self)
-	save.pack(self)
 	print("Writing save to ", save_path)
 	ResourceSaver.save(save, save_path)
+	print("Done!")

src/world/world.tscn

@@ -3,15 +3,15 @@
 [ext_resource type="Script" uid="uid://cgqmhtemibxc5" path="res://src/world/world.gd" id="1_1k4gi"]
 [ext_resource type="Resource" uid="uid://tgac5tnfx56r" path="res://src/world/world_manager.tres" id="2_5kmgb"]
 [ext_resource type="PackedScene" uid="uid://byvjsvavbg5xe" path="res://src/ui/menus/pause_menu/pause_menu.tscn" id="2_6fy3g"]
-[ext_resource type="PackedScene" uid="uid://bov4ok76woyc" path="res://levels/ghost_ship/ghost_ship.tscn" id="2_jte2u"]
 [ext_resource type="Resource" uid="uid://0i72bf8ip1lx" path="res://src/world/spook_manager.tres" id="3_l0av5"]
+[ext_resource type="PackedScene" uid="uid://b8rv6dg4tgaeb" path="res://src/world/gunk_node/mechanic_test.tscn" id="4_l0av5"]
 [ext_resource type="PackedScene" uid="uid://c0uitm5cg88h1" path="res://src/ui/menus/kill_screen/kill_screen.tscn" id="6_l0av5"]
 
 [node name="World" type="Node"]
 script = ExtResource("1_1k4gi")
 manager = ExtResource("2_5kmgb")
 spook_manager = ExtResource("3_l0av5")
-initial_level = ExtResource("2_jte2u")
+initial_level = ExtResource("4_l0av5")
 pause_scene = ExtResource("2_6fy3g")
 kill_screen_scene = ExtResource("6_l0av5")
 

src/world/world_item/world_item.gd

@@ -32,3 +32,13 @@ func _on_interactive_activated() -> void:
 	Player.instance.add_item(item)
 	# TODO: animation, sfx on collect?
 	queue_free()
+
+
+func serialize() -> Dictionary:
+	# Nothing to serialize, but we need a placeholder value to show we haven't been destroyed.
+	return {}
+
+
+func deserialize(_state: Dictionary) -> void:
+	# Nothing to deserialize, but we won't be freed!
+	pass

src/world/world_item/world_item.tscn

@@ -6,7 +6,7 @@
 [sub_resource type="SphereShape3D" id="SphereShape3D_0mein"]
 radius = 0.25
 
-[node name="WorldItem" type="MeshInstance3D"]
+[node name="WorldItem" type="MeshInstance3D" groups=["Persistent"]]
 script = ExtResource("1_sptcj")
 
 [node name="Interactive" type="StaticBody3D" parent="."]