diff --git a/surface/GasVentField.gd b/surface/GasVentField.gd
index e2476ce..4f5b381 100644
--- a/surface/GasVentField.gd
+++ b/surface/GasVentField.gd
@@ -9,7 +9,23 @@ const RESOURCE_PICKUP_VFX = preload("res://vfx/ResourcePickupVFX.gd")
 
 @export var fleet_path: NodePath = NodePath("../Fleet")
 @onready var fleet: Node2D = get_node(fleet_path)
+const SOURCE_COLOUR: Color = Color(0.85, 0.52, 1.0)
+const CORE_COLOUR: Color = Color(0.15, 0.03, 0.22)
+# Offsets from a vent's centre, and each bubble's radius.
+const SOURCE_BUBBLES: Array = [
+	[Vector2(-20.0, 8.0), 20.0],
+	[Vector2(18.0, 14.0), 27.0],
+	[Vector2(17.0, -22.0), 15.0],
+]
+
+const BUBBLES_PER_VENT: int = 4
+const BUBBLE_MIN_RADIUS: float = 5.0
+const BUBBLE_MAX_RADIUS: float = 14.0
+const EMISSION_COLOUR: Color = Color(0.92, 0.68, 1.0)
+
 var vents: Array[Vector2] = []
+# One row of rising-bubble pieces per vent.
+var bubbles: Array = []
 var progress: float = 0.0
 var emission_phase: float = 0.0
 func _ready() -> void:
@@ -24,10 +40,73 @@ func _ready() -> void:
 	var rng := RandomNumberGenerator.new()
 	rng.seed = hash(GameState.planet_id if GameState.planet_id != "" else GameState.planet_name)
 	for i in range(6): vents.append(Vector2(rng.randf_range(-800,800), rng.randf_range(-650,650)))
-	queue_redraw()
+	_build_sources()
+	_build_bubbles()
+	_place_bubbles()
+
+
+# The sources never move, never change colour and never fade - they were
+# simply being re-tessellated every frame alongside the bubbles rising out of
+# them, because one _draw() covered both. Eighteen glowing polygons a frame,
+# each of which NeonDraw expands into four antialiased polylines. Rasterised
+# once into a piece each now, per the rule issues #6 and #10 set.
+func _build_sources() -> void:
+	for vent in vents:
+		var piece: NeonPiece = NeonPiece.create(self, vent, SOURCE_COLOUR)
+		piece.core_color = CORE_COLOUR
+		piece.z_index = -1
+		for bubble in SOURCE_BUBBLES:
+			var ring := PackedVector2Array()
+			for i in range(12):
+				var angle: float = TAU * float(i) / 12.0
+				ring.append(Vector2(bubble[0]) + Vector2(cos(angle), sin(angle)) * float(bubble[1]))
+			piece.add_polygon(ring, 0.9, 0.6)
+
+
+# One piece per rising bubble, built as a UNIT circle and thereafter only
+# moved, scaled and faded. The bubble genuinely changes size and opacity as
+# it climbs, which is why this used to redraw - but size is scale and opacity
+# is modulate, and neither needs the geometry rebuilding.
+func _build_bubbles() -> void:
+	for vent in vents:
+		var row: Array = []
+		for i in range(BUBBLES_PER_VENT):
+			var piece: NeonPiece = NeonPiece.create(self, vent, EMISSION_COLOUR)
+			piece.core_color = CORE_COLOUR
+			piece.z_index = -1
+			# Built at the LARGEST size a bubble reaches and scaled DOWN,
+			# never up. Scaling a piece scales its stroke with it, and a unit
+			# circle blown up to radius 14 took NeonDraw's widths with it -
+			# a hundred pixels of glow around a fourteen pixel bubble, which
+			# rendered as a bright blob rather than a bubble. Downward, the
+			# stroke only ever thins, which is what a smaller bubble wants.
+			var ring := PackedVector2Array()
+			for point in range(10):
+				var angle: float = TAU * float(point) / 10.0
+				ring.append(Vector2(cos(angle), sin(angle)) * BUBBLE_MAX_RADIUS)
+			piece.add_polygon(ring, 0.75, 0.45)
+			row.append(piece)
+		bubbles.append(row)
+
+
+# Where one bubble sits, how big it is and how faded, for a point in its
+# climb. Unchanged arithmetic - only the thing it is applied to changed.
+func _place_bubbles() -> void:
+	for v in range(vents.size()):
+		for i in range(BUBBLES_PER_VENT):
+			var travel: float = fmod(emission_phase + float(i) * 0.25, 1.0)
+			var piece: NeonPiece = bubbles[v][i]
+			piece.position = vents[v] + Vector2(
+				sin((travel + float(i)) * TAU) * 11.0,
+				-48.0 - travel * 92.0)
+			var radius: float = lerpf(BUBBLE_MIN_RADIUS, BUBBLE_MAX_RADIUS, travel)
+			var k: float = radius / BUBBLE_MAX_RADIUS
+			piece.scale = Vector2(k, k)
+			piece.modulate.a = 1.0 - travel * 0.72
 func _process(delta: float) -> void:
 	emission_phase = fmod(emission_phase + delta * 0.55, 1.0)
-	queue_redraw()
+	# Node properties only. Nothing is rasterised after the first frame.
+	_place_bubbles()
 	for vent in vents:
 		if fleet.get_centroid().distance_to(vent) < 90.0:
 			progress += delta
@@ -42,43 +121,3 @@ func _process(delta: float) -> void:
 					to_global(vent), GameState.RESOURCE_GAS, taken)
 			return
 	progress = 0.0
-func _draw() -> void:
-	for vent in vents:
-		_draw_gas_source(vent)
-		_draw_emission(vent)
-
-
-func _draw_gas_source(centre: Vector2) -> void:
-	var colour := Color(0.85, 0.52, 1.0)
-	var core := Color(0.15, 0.03, 0.22)
-	var bubbles: Array = [
-		[centre + Vector2(-20.0, 8.0), 20.0],
-		[centre + Vector2(18.0, 14.0), 27.0],
-		[centre + Vector2(17.0, -22.0), 15.0],
-	]
-	for bubble in bubbles:
-		var ring := PackedVector2Array()
-		for i in range(12):
-			var angle: float = TAU * float(i) / 12.0
-			ring.append(bubble[0] + Vector2(cos(angle), sin(angle)) * float(bubble[1]))
-		NeonDraw.draw_glowing_polygon(self, ring, colour, 0.9, core, 0.6)
-
-
-func _draw_emission(centre: Vector2) -> void:
-	# Small bubbles continuously rise out of every source. This remains
-	# animated even when the fleet is not collecting, so the vent reads as
-	# an active gas generator rather than a static decoration.
-	var core := Color(0.15, 0.03, 0.22)
-	for i in range(4):
-		var travel: float = fmod(emission_phase + float(i) * 0.25, 1.0)
-		var bubble_centre := centre + Vector2(
-			sin((travel + float(i)) * TAU) * 11.0,
-			-48.0 - travel * 92.0
-		)
-		var radius: float = lerpf(5.0, 14.0, travel)
-		var colour := Color(0.92, 0.68, 1.0, 1.0 - travel * 0.72)
-		var ring := PackedVector2Array()
-		for point in range(10):
-			var angle: float = TAU * float(point) / 10.0
-			ring.append(bubble_centre + Vector2(cos(angle), sin(angle)) * radius)
-		NeonDraw.draw_glowing_polygon(self, ring, colour, 0.75, core, 0.45)
diff --git a/vfx/NeonPiece.gd b/vfx/NeonPiece.gd
index 906a510..25e00ba 100644
--- a/vfx/NeonPiece.gd
+++ b/vfx/NeonPiece.gd
@@ -34,8 +34,9 @@ static func create(parent: Node, at: Vector2, colour: Color, alpha: float = 1.0)
 	return piece
 
 
-func add_polygon(points: PackedVector2Array, piece_pulse: float = 1.0) -> void:
-	polygons.append({"points": points, "pulse": piece_pulse})
+func add_polygon(points: PackedVector2Array, piece_pulse: float = 1.0,
+		width: float = 1.0) -> void:
+	polygons.append({"points": points, "pulse": piece_pulse, "width": width})
 
 
 func add_path(points: PackedVector2Array, piece_pulse: float = 1.0,
@@ -49,7 +50,8 @@ func add_line(from: Vector2, to: Vector2, width: float, piece_pulse: float = 1.0
 
 func _draw() -> void:
 	for poly in polygons:
-		NeonDraw.draw_glowing_polygon(self, poly.points, glow_color, poly.pulse * pulse, core_color)
+		NeonDraw.draw_glowing_polygon(self, poly.points, glow_color,
+			poly.pulse * pulse, core_color, float(poly.get("width", 1.0)))
 	for path in paths:
 		NeonDraw.draw_glowing_path(self, path.points, glow_color,
 			path.pulse * pulse, path.width, core_color)