Gate enemies behind a detection range instead of instant omniscient pursuit (#69)

Chasers (EnemyPursuitComponent) and snipers (EnemyStandoffComponent)
used to beeline/close in from anywhere on the map the instant they
spawned - no matter how far the fleet was, which read as omniscient
rather than alert. Both now sit idle until the fleet is within their
own detection_range. Artillery's slow drift is gated the same way, but
reuses its own existing fire_range rather than a new tunable - outside
its firing envelope it has nothing to be drifting toward yet.

The enemy mothership deliberately keeps the opposite behaviour: it is
meant to read as a persistent, unavoidable stalking threat, not a
local sentry, so it gets its own EnemyPursuitComponentMothership.tscn
variant with an effectively unlimited detection_range - the same
scene-variant pattern EnemySpawnerComponentChaser/Artillery already
use for per-definition property overrides on a shared component script.

EnemyArtilleryComponent.gd

@@ -56,6 +56,11 @@ func _drift(enemy: Node2D, delta: float) -> void:
 	if fleet == null or fleet.ships.is_empty():
 		return
 	var to_fleet: Vector2 = fleet.get_centroid() - enemy.position
+	# #69: gated by the same fire_range it already shells within, rather
+	# than a second tunable that could drift out of sync - outside its own
+	# firing envelope it has nothing to be drifting toward yet.
+	if to_fleet.length() > fire_range:
+		return
 	if to_fleet.length() < 1.0:
 		return
 	enemy.position += to_fleet.normalized() * drift_speed * delta

EnemyPursuitComponent.gd

@@ -7,11 +7,20 @@ extends Node
 var capability_id: String = "pursuit"
 var velocity: Vector2 = Vector2.ZERO
 
+# #69: used to beeline from anywhere on the map the instant it spawned,
+# which read as omniscient rather than alert. Idle until the fleet actually
+# comes within this radius. A persistent stalking threat wants the opposite
+# of this - see EnemyPursuitComponentMothership.tscn, which overrides it to
+# an effectively unlimited value for the mothership's own instance.
+@export var detection_range: float = 850.0
+
 
 func tick(delta: float) -> void:
 	var enemy: Node2D = get_parent()
-	var target_pos: Vector2 = _nearest_ship_position(enemy)
-	var to_target: Vector2 = target_pos - enemy.position
+	var target: Node2D = _nearest_ship(enemy)
+	if target == null or enemy.position.distance_to(target.position) > detection_range:
+		return
+	var to_target: Vector2 = target.position - enemy.position
 
 	if to_target.length() > 1.0:
 		var desired_velocity: Vector2 = to_target.normalized() * enemy.speed
@@ -23,10 +32,10 @@ func tick(delta: float) -> void:
 		enemy.rotation = lerp_angle(enemy.rotation, target_angle, enemy.rotation_speed * delta)
 
 
-func _nearest_ship_position(enemy: Node2D) -> Vector2:
+func _nearest_ship(enemy: Node2D) -> Node2D:
 	var fleet: Node2D = get_tree().get_first_node_in_group("player_fleet")
 	if fleet == null or fleet.ships.is_empty():
-		return enemy.position
+		return null
 
 	var nearest: Node2D = fleet.ships[0]
 	var best_dist: float = enemy.position.distance_to(nearest.position)
@@ -35,4 +44,4 @@ func _nearest_ship_position(enemy: Node2D) -> Vector2:
 		if d < best_dist:
 			best_dist = d
 			nearest = ship
-	return nearest.position
+	return nearest

EnemyPursuitComponentMothership.tscn

@@ -0,0 +1,7 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://EnemyPursuitComponent.gd" id="1"]
+
+[node name="EnemyPursuitComponentMothership" type="Node"]
+script = ExtResource("1")
+detection_range = 1000000.0

EnemyStandoffComponent.gd

@@ -11,6 +11,10 @@ var capability_id: String = "standoff"
 
 @export var preferred_range: float = 620.0
 @export var retreat_range_factor: float = 0.75
+# #69: kept comfortably beyond preferred_range so it still has room to close
+# in before settling at stand-off distance, but the fleet has to actually be
+# somewhere on the board first - see EnemyPursuitComponent's identical fix.
+@export var detection_range: float = 1200.0
 
 var velocity: Vector2 = Vector2.ZERO
 
@@ -22,7 +26,7 @@ func tick(delta: float) -> void:
 		return
 	var to_target: Vector2 = target.position - enemy.position
 	var distance: float = to_target.length()
-	if distance < 1.0:
+	if distance < 1.0 or distance > detection_range:
 		return
 	var direction: Vector2 = to_target / distance
 	var retreat_range: float = preferred_range * retreat_range_factor

MothershipEnemyDefinition.tres

@@ -1,7 +1,7 @@
 [gd_resource type="Resource" script_class="EnemyDefinition" load_steps=6 format=3]
 
 [ext_resource type="Script" path="res://EnemyDefinition.gd" id="1"]
-[ext_resource type="PackedScene" path="res://EnemyPursuitComponent.tscn" id="2"]
+[ext_resource type="PackedScene" path="res://EnemyPursuitComponentMothership.tscn" id="2"]
 [ext_resource type="PackedScene" path="res://EnemySpawnerComponentChaser.tscn" id="3"]
 [ext_resource type="PackedScene" path="res://EnemySpawnerComponentArtillery.tscn" id="4"]
 [ext_resource type="PackedScene" path="res://EnemyBigLaserComponent.tscn" id="5"]

tests/test_enemy_detection_range.gd

@@ -0,0 +1,129 @@
+extends SceneTree
+
+# Headless gameplay test: run with
+#   godot --headless -s res://tests/test_enemy_detection_range.gd
+# Forgejo #69: enemies used to beeline toward the fleet from anywhere on the
+# map the instant they spawned. Chasers (EnemyPursuitComponent) and snipers
+# (EnemyStandoffComponent) now sit idle until the fleet is within their own
+# detection_range; the enemy mothership deliberately keeps an (effectively)
+# unlimited range instead, since it is meant to read as a persistent,
+# unavoidable stalking threat rather than a local sentry.
+#
+# Covers:
+#   A. a chaser beyond detection_range does not move at all
+#   B. the same chaser, once the fleet is within range, closes in
+#   C. a sniper beyond detection_range does not move either
+#   D. the enemy mothership closes in even from far beyond a chaser's range
+
+var game_state: Node
+var main: Node
+var fleet: Node
+var chaser: Node
+var sniper: Node
+var mothership: Node
+var chaser_start: Vector2
+var sniper_start: Vector2
+var mothership_start: Vector2
+var stage: int = 0
+var elapsed: float = 0.0
+
+
+func _initialize() -> void:
+	game_state = root.get_node("GameState")
+	game_state.buildings.clear()
+	game_state.extractors.clear()
+	game_state.transporters.clear()
+	game_state.reset_progression()
+	main = load("res://Main.tscn").instantiate()
+	root.add_child(main)
+	fleet = main.get_node("Fleet")
+
+
+func _process(delta: float) -> bool:
+	elapsed += delta
+	match stage:
+		0:
+			if elapsed < 0.2:
+				return false
+			main.get_node("EnemySpawner").set_process(false)
+			main.get_node("AsteroidField").set_process(false)
+			for a in get_nodes_in_group("asteroids"):
+				a.queue_free()
+			fleet.spawn_ships(1, Vector2.ZERO)
+
+			# --- A. beyond detection_range: no movement at all ---------------
+			chaser = load("res://Enemy.tscn").instantiate()
+			chaser.enemy_id = "chaser"
+			var pursuit: Node = null
+			main.add_child(chaser)
+			pursuit = chaser.get_component("pursuit")
+			chaser.position = fleet.get_centroid() + Vector2(pursuit.detection_range + 300.0, 0.0)
+			chaser_start = chaser.position
+
+			sniper = load("res://Enemy.tscn").instantiate()
+			sniper.enemy_id = "sniper"
+			main.add_child(sniper)
+			var standoff: Node = sniper.get_component("standoff")
+			sniper.position = fleet.get_centroid() + Vector2(0.0, standoff.detection_range + 300.0)
+			sniper_start = sniper.position
+
+			elapsed = 0.0
+			stage = 1
+			return false
+		1:
+			if elapsed < 1.0:
+				return false
+			var chaser_moved: float = chaser.position.distance_to(chaser_start)
+			var sniper_moved: float = sniper.position.distance_to(sniper_start)
+			print("beyond range for 1.0s: chaser moved %.1f, sniper moved %.1f" % [chaser_moved, sniper_moved])
+			if chaser_moved > 1.0:
+				return _fail("a chaser beyond detection_range moved %.1f - it should sit idle" % chaser_moved)
+			if sniper_moved > 1.0:
+				return _fail("a sniper beyond detection_range moved %.1f - it should sit idle" % sniper_moved)
+
+			# --- B. bring the chaser within range, it should now close in ----
+			var pursuit: Node = chaser.get_component("pursuit")
+			chaser.position = fleet.get_centroid() + Vector2(pursuit.detection_range * 0.5, 0.0)
+			chaser_start = chaser.position
+			elapsed = 0.0
+			stage = 2
+			return false
+		2:
+			if elapsed < 1.0:
+				return false
+			var chaser_moved: float = chaser.position.distance_to(chaser_start)
+			print("within range for 1.0s: chaser moved %.1f" % chaser_moved)
+			if chaser_moved < 20.0:
+				return _fail("a chaser within detection_range did not close in (moved %.1f)" % chaser_moved)
+			print("chaser correctly idle beyond range, closes in once inside it")
+
+			# --- D. the mothership closes in from far beyond a chaser's range -
+			mothership = load("res://Enemy.tscn").instantiate()
+			mothership.enemy_id = "enemy_mothership"
+			main.add_child(mothership)
+			var mother_pursuit: Node = mothership.get_component("pursuit")
+			if mother_pursuit.detection_range < 50000.0:
+				return _fail("the mothership's pursuit range is not effectively unlimited (%f)" \
+					% mother_pursuit.detection_range)
+			mothership.position = fleet.get_centroid() + Vector2(5000.0, 0.0)
+			mothership_start = mothership.position
+			elapsed = 0.0
+			stage = 3
+			return false
+		3:
+			if elapsed < 1.0:
+				return false
+			var mothership_moved: float = mothership.position.distance_to(mothership_start)
+			print("mothership 5000 units out, 1.0s: moved %.1f" % mothership_moved)
+			if mothership_moved < 5.0:
+				return _fail("the mothership did not close in from far away (moved %.1f)" % mothership_moved)
+			print("TEST_ENEMY_DETECTION_RANGE: PASS")
+			quit(0)
+			return true
+	return false
+
+
+func _fail(message: String) -> bool:
+	print("TEST_ENEMY_DETECTION_RANGE: FAIL (%s)" % message)
+	quit(1)
+	return true