Added basic day night cycle

scenes/Grid/grid_field.tscn

@@ -66,6 +66,7 @@ cast_shadow = 0
 mesh = SubResource("ArrayMesh_q3k88")
 
 [node name="DirectionalLight3D" type="DirectionalLight3D" parent="."]
+unique_name_in_owner = true
 transform = Transform3D(0.707107, -0.5, 0.5, 0, 0.707107, 0.707107, -0.707107, -0.5, 0.5, 0, 5, 0)
 shadow_enabled = true
 

scenes/Grid/grid_plane_manager.gd

@@ -71,6 +71,31 @@ var _ground_padding: float = 20.0
 	get:
 		return _ground_padding
 
+var _day_length_hours: float = 12.0
+@export_range(1.0, 48.0, 0.5) var day_length_hours: float = 12.0:
+	set(value):
+		value = max(value, 1.0)
+		if is_equal_approx(value, _day_length_hours):
+			return
+		_day_length_hours = value
+		_time_of_day_hours = clamp(_time_of_day_hours, 0.0, _day_length_hours)
+		_apply_sun_lighting()
+	get:
+		return _day_length_hours
+
+var _seconds_per_game_hour: float = 60.0
+@export_range(1.0, 600.0, 1.0) var real_seconds_per_game_hour: float = 60.0:
+	set(value):
+		value = clamp(value, 1.0, 600.0)
+		if is_equal_approx(value, _seconds_per_game_hour):
+			return
+		_seconds_per_game_hour = value
+	get:
+		return _seconds_per_game_hour
+
+@export_range(0.0, 48.0, 0.25) var start_time_of_day_hours: float = 6.0
+var _time_of_day_hours: float = 0.0
+
 var _zoom_factor: float = 1.0
 var _zoom_min_internal: float = 0.5
 var _zoom_max_internal: float = 3.0
@@ -128,6 +153,7 @@ const _SQRT3 := 1.7320508075688772
 @onready var _grid_lines: MeshInstance3D = %GridLines
 @onready var _camera: Camera3D = %Camera3D
 @onready var _hover_highlight: MeshInstance3D = %HoverHighlight
+@onready var _sun_light: DirectionalLight3D = %DirectionalLight3D
 
 var _grid_size: Vector2 = Vector2.ZERO
 var _cells: Dictionary = {}
@@ -138,6 +164,7 @@ var _hex_center_offset_local: Vector3 = Vector3.ZERO
 func _ready() -> void:
 	set_process(true)
 	_zoom_factor = clamp(_zoom_factor, _zoom_min_internal, _zoom_max_internal)
+	_time_of_day_hours = clamp(start_time_of_day_hours, 0.0, _day_length_hours)
 	_queue_rebuild()
 
 func get_cells() -> Dictionary:
@@ -181,6 +208,7 @@ func _rebuild_grid() -> void:
 	_update_highlight_mesh()
 	_update_camera_view()
 	_update_ground_assets()
+	_apply_sun_lighting()
 	emit_signal("grid_layout_changed", _cells)
 
 func _update_ground_assets() -> void:
@@ -428,11 +456,45 @@ func _compute_required_ground_size() -> Vector2:
 	var padding_vec := Vector2.ONE * _ground_padding
 	return (half_extents + padding_vec) * 2.0
 
+func _update_day_cycle(delta: float) -> void:
+	if _day_length_hours <= 0.0 or _seconds_per_game_hour <= 0.0:
+		return
+	_time_of_day_hours = fposmod(_time_of_day_hours + delta / _seconds_per_game_hour, _day_length_hours)
+	_apply_sun_lighting()
+
+func _apply_sun_lighting() -> void:
+	if not is_instance_valid(_sun_light):
+		return
+	if _day_length_hours <= 0.0:
+		return
+	var cycle: float = 0.0
+	if _day_length_hours > 0.0:
+		cycle = fposmod(_time_of_day_hours / _day_length_hours, 1.0)
+	var sun_angle: float = cycle * TAU
+	var rotation_axis: Vector3 = Vector3(1.0, 0.0, -1.0).normalized()
+	if rotation_axis.length() == 0.0:
+		rotation_axis = Vector3.RIGHT
+	var direction: Vector3 = Vector3.UP.rotated(rotation_axis, sun_angle)
+	direction = direction.rotated(Vector3.UP, deg_to_rad(35.0)).normalized()
+	var target: Vector3 = global_transform.origin
+	var sun_distance: float = 60.0
+	var sun_position: Vector3 = target - direction * sun_distance
+	_sun_light.look_at_from_position(sun_position, target, Vector3.UP)
+	var daylight: float = clamp(direction.y * 0.5 + 0.5, 0.0, 1.0)
+	var dawn_color: Color = Color(0.95, 0.58, 0.32)
+	var night_color: Color = Color(0.12, 0.18, 0.35)
+	var day_color: Color = Color(1.0, 0.96, 0.88)
+	var warm_mix: Color = dawn_color.lerp(day_color, clamp((daylight - 0.25) / 0.5, 0.0, 1.0))
+	_sun_light.light_color = night_color.lerp(warm_mix, daylight)
+	_sun_light.light_energy = lerp(0.05, 1.25, daylight)
+	_sun_light.shadow_enabled = daylight > 0.1
+
 func _process(_delta: float) -> void:
 	if Engine.is_editor_hint():
 		return
 	var mouse_position: Vector2 = get_viewport().get_mouse_position()
 	_update_hovered_cell(mouse_position)
+	_update_day_cycle(_delta)
 
 func _unhandled_input(event: InputEvent) -> void:
 	if Engine.is_editor_hint():
@@ -445,7 +507,7 @@ func _unhandled_input(event: InputEvent) -> void:
 			_adjust_zoom(_zoom_step_internal)
 
 func _adjust_zoom(delta: float) -> void:
-	var previous := _zoom_factor
+	var previous: float = _zoom_factor
 	_zoom_factor = clamp(_zoom_factor + delta, _zoom_min_internal, _zoom_max_internal)
 	if is_equal_approx(previous, _zoom_factor):
 		return