#89: the default gun bends onto a target near the aimed heading

Aiming with a thumb on a stick is never exact, and at 950 units a couple of
degrees is a long miss. A shot fired roughly toward an enemy now goes at it.

28 degrees of cone, chosen so that pointing at something hits it while the
shot still visibly goes where the player pointed. Past about 45 the gun starts
picking its own targets, which is the behaviour #80 deliberately removed.

Enemies only, never asteroids. Snapping onto a rock while the player is trying
to hit the thing shooting at them would be the assist working against them,
and rocks are large and stationary enough to hit on purpose.

The aim guide is drawn through the SAME helper the gun fires through, so the
dotted line bends with the shot. A guide showing the raw stick heading while
the bolt took an assisted one would be the same class of mismatch #86 removed
between the guide's length and a bolt's actual reach - and this one would have
been harder to notice, because the line would look right most of the time.

Range 620 -> 950, the other half of the ticket.

Also swept the project root again: Godot keeps resurrecting pre-#84 copies of
moved files there from its own cache. None this time.

Suite 120/120.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_aim_assist.gd

@@ -0,0 +1,146 @@
+extends SceneTree
+
+# Headless gameplay test: run with
+#   godot --headless -s res://tests/test_aim_assist.gd
+# Forgejo #89: a shot fired roughly toward an enemy bends onto it, so aiming
+# with a thumb on a stick does not have to be exact.
+#
+# Covers:
+#   A. an enemy just off the aimed heading is picked up, and the bolt flies at
+#      IT rather than where the stick pointed
+#   B. an enemy far off the heading is not - past the cone the shot goes where
+#      the player pointed, or the gun would be choosing its own targets again,
+#      which is exactly what #80 took away
+#   C. the NEAREST candidate inside the cone wins
+#   D. asteroids are never assisted onto. Snapping to a rock while the player
+#      is trying to hit the thing shooting at them is the assist working
+#      against them
+#   E. the aim guide follows the assist, so the dotted line keeps telling the
+#      truth about where fire is going
+
+var game_state: Node
+var main: Node
+var fleet: Node
+var controller: Node
+var weapon: Node
+var shooter: Node2D
+var stage: int = 0
+var elapsed: float = 0.0
+
+const AIM := Vector2(1.0, 0.0)
+
+
+func _initialize() -> void:
+	game_state = root.get_node("GameState")
+	game_state.buildings.clear()
+	game_state.extractors.clear()
+	game_state.reset_progression()
+	main = load("res://world/Main.tscn").instantiate()
+	root.add_child(main)
+	current_scene = main
+	fleet = main.get_node("Fleet")
+	controller = main.get_node("FireStickController")
+
+
+func _clear() -> void:
+	for node in get_nodes_in_group("enemies") + get_nodes_in_group("asteroids") \
+			+ get_nodes_in_group("player_projectiles"):
+		if is_instance_valid(node):
+			node.free()
+
+
+func _enemy_at(offset: Vector2) -> Node2D:
+	var enemy: Node2D = load("res://enemies/Enemy.tscn").instantiate()
+	enemy.position = shooter.global_position + offset
+	main.add_child(enemy)
+	enemy.speed = 0.0
+	return enemy
+
+
+func _heading(direction: Vector2) -> Vector2:
+	var script: Script = load("res://vessels/VesselWeaponComponent.gd")
+	return script.assisted_heading(self, shooter.global_position, direction,
+		weapon.fire_range)
+
+
+func _process(delta: float) -> bool:
+	elapsed += delta
+	if stage != 0:
+		return false
+	if elapsed < 0.3:
+		return false
+	stage = 1
+
+	main.get_node("EnemySpawner").set_process(false)
+	main.get_node("AsteroidField").set_process(false)
+	_clear()
+	fleet.spawn_ships(1, Vector2.ZERO, PackedStringArray([GameState.VESSEL_INTERCEPTOR]))
+	shooter = fleet.ships[0]
+	weapon = shooter.get_component("weapon")
+
+	# --- A. just off the heading is picked up -----------------------------
+	var near_angle: float = deg_to_rad(18.0)
+	var target: Node2D = _enemy_at(Vector2(600.0, 0.0).rotated(near_angle))
+	var assisted: Vector2 = _heading(AIM)
+	var wanted: Vector2 = (target.global_position - shooter.global_position).normalized()
+	if assisted.distance_to(wanted) > 0.01:
+		return _fail("an enemy 18 degrees off the heading was not picked up (heading %s)" % assisted)
+	print("an enemy 18 degrees off the aim is picked up")
+
+	# --- B. far off the heading is not ------------------------------------
+	_clear()
+	_enemy_at(Vector2(600.0, 0.0).rotated(deg_to_rad(55.0)))
+	assisted = _heading(AIM)
+	if assisted.distance_to(AIM) > 0.01:
+		return _fail("an enemy 55 degrees off the heading was still picked up (heading %s)" % assisted)
+	print("an enemy 55 degrees off the aim is ignored - the shot goes where it was aimed")
+
+	# --- C. the nearest inside the cone wins ------------------------------
+	_clear()
+	var far_target: Node2D = _enemy_at(Vector2(800.0, 0.0).rotated(deg_to_rad(5.0)))
+	var close_target: Node2D = _enemy_at(Vector2(300.0, 0.0).rotated(deg_to_rad(20.0)))
+	assisted = _heading(AIM)
+	var to_close: Vector2 = (close_target.global_position - shooter.global_position).normalized()
+	var to_far: Vector2 = (far_target.global_position - shooter.global_position).normalized()
+	if assisted.distance_to(to_close) > 0.01:
+		return _fail("the assist chose the enemy at 800 over the one at 300 (heading %s, close %s, far %s)" \
+			% [assisted, to_close, to_far])
+	print("with two in the cone, the nearer one wins")
+
+	# --- D. never onto an asteroid ----------------------------------------
+	_clear()
+	var rock: Node2D = load("res://world/Asteroid.tscn").instantiate()
+	rock.position = shooter.global_position + Vector2(400.0, 0.0).rotated(deg_to_rad(15.0))
+	main.add_child(rock)
+	assisted = _heading(AIM)
+	if assisted.distance_to(AIM) > 0.01:
+		return _fail("the assist snapped onto an asteroid (heading %s)" % assisted)
+	print("asteroids are never assisted onto")
+
+	# --- E. the guide follows the assist ----------------------------------
+	_clear()
+	var guide_target: Node2D = _enemy_at(Vector2(500.0, 0.0).rotated(deg_to_rad(20.0)))
+	controller.aim(AIM)
+	controller.aim_direction = AIM
+	var guided: Vector2 = load("res://vessels/VesselWeaponComponent.gd").assisted_heading(
+		self, fleet.get_centroid(), controller.aim_direction, controller.guide_range())
+	var from_fleet: Vector2 = (guide_target.global_position - fleet.get_centroid()).normalized()
+	if guided.distance_to(from_fleet) > 0.02:
+		return _fail("the aim guide does not follow the assist (guide %s, target %s)" % [guided, from_fleet])
+	# And the guide must be drawn from that same helper, not a copy of the maths.
+	var source: FileAccess = FileAccess.open("res://controllers/FireStickController.gd", FileAccess.READ)
+	var text: String = source.get_as_text()
+	source.close()
+	if "assisted_heading" not in text:
+		return _fail("FireStickController draws its guide without the assist, so the line and the shot would diverge")
+	print("the aim guide is drawn along the assisted heading, from the same helper the gun uses")
+
+	print("TEST_AIM_ASSIST: PASS")
+	quit(0)
+	return true
+
+
+func _fail(message: String) -> bool:
+	print("TEST_AIM_ASSIST: FAIL (%s)" % message)
+	quit(1)
+	return true