Add transfer amounts and active gas vents

RockField.gd

@@ -26,6 +26,12 @@ var rng: RandomNumberGenerator = RandomNumberGenerator.new()
 
 
 func _ready() -> void:
+	# Gas giants have their own gas vents and must never receive ore pickups.
+	# This check happens before the initial population pass, unlike merely
+	# hiding the field later from PlanetSurfaceController.
+	if GameState.planet_type == "gas_giant":
+		set_process(false)
+		return
 	rng.randomize()
 	# Populate immediately rather than waiting out the first interval, so
 	# the surface isn't visibly empty for half a second on arrival.
@@ -65,7 +71,7 @@ func _spawn_rock(centre: Vector2) -> void:
 	var rock: Area2D = rock_scene.instantiate()
 	rock.position = centre + Vector2(cos(angle), sin(angle)) * distance
 	rock.build_shape(rng.randi())
-	# Deferred: update_rocks() runs from _ready(), and Godot refuses a
-	# direct add_child() while the tree is still setting up children.
-	get_parent().add_child.call_deferred(rock)
+	# Keep pickups under this field so its visibility and lifecycle really
+	# own them. Deferred is still required because this can run from _ready().
+	add_child.call_deferred(rock)
 	rocks.append(rock)