Add a double laser projectile effect.

This effect adds an identical lazer ouput offset from the original
laser.
It also makes some modifications to how the firing mechanism and
effects dispatch is handled, to make it easier to offload effect
mechanism management to each effect.

projectiles/double_laser.gd

@@ -0,0 +1,30 @@
+class_name EffectDoubleLaser
+extends ProjectileEffect
+
+var Projectile : PackedScene = preload("res://units/projectile.tscn")
+@export var laser_offset = Vector2(0, -50)
+const is_double_laser = true
+
+func check_not_double_laser(effect: ProjectileEffect) -> bool:
+	# TODO:: Filter on type? This implementation is Bad
+	if "is_double_laser" in effect:
+		return not effect.is_double_laser
+	return true
+
+func modify_creation(owner: Node, projectile_effects: Array[ProjectileEffect], transform: Transform2D):
+		var p = Projectile.instantiate()
+		# TODO:: Stacking double-lasers? would mean we only want to filter 1 out of this list.
+		var non_recursive_effects = projectile_effects.filter(check_not_double_laser)
+		var doubled_transform = transform
+		# TODO:: Do we want to offset the laser, or do we want to angle out of the same point of origin?
+		doubled_transform.origin += laser_offset
+		p.spawn(owner, non_recursive_effects, doubled_transform)
+
+# Called when the node enters the scene tree for the first time.
+func _ready():
+	Projectile = load("res://units/projectile.tscn")
+# Called when the node enters the scene tree for the first time.
+
+# Called every frame. 'delta' is the elapsed time since the previous frame.
+func _process(delta):
+	pass

projectiles/double_laser.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://dgp68vbl25onx"]
+
+[ext_resource type="Script" path="res://projectiles/double_laser.gd" id="1_wqupk"]
+
+[node name="DoubleLaser" type="Node"]
+script = ExtResource("1_wqupk")

projectiles/projectile_effect.gd

@@ -25,7 +25,7 @@ enum MODIFICATION_TYPE {
 
 # Modify the logic that adds the projectile as a child to the scene.
 # This can be used to change spawn locations, quantities, etc.
-func modify_creation(owner: Node):
+func modify_creation(owner: Node, projectile_effects: Array[ProjectileEffect], transform: Transform2D):
 	pass
 
 # Modify the physics logic of the projectile. This function will be called

units/player.gd

@@ -9,13 +9,28 @@ const HORIZONTAL_BUFFER = 75
 
 @export var Projectile : PackedScene
 @onready var projectile_spawner = $ProjectileSpawner
-
 var projectile_effects: Array[ProjectileEffect] = []
 
 # Called when the node enters the scene tree for the first time.
 func _ready():
 	Projectile = load("res://units/projectile.tscn")
+	_add_test_effects()
+
+func _add_test_effects():
+		# Debugging -- these should be added to the list via some user interaction instead.
+	var double_laser = load("res://projectiles/double_laser.tscn")
+	# TODO:: Not even sure if adding to the scene tree here is necessary.
+	#    It's necessary now just to trigger projectile_effect._ready, but the
+	#    utility functions will get called regardless of its presense in the scene
+	#    tree, as long as thy're in the top-level projectile_effects Array.
+	add_child(double_laser.instantiate())
+	projectile_effects.append(EffectDoubleLaser.new())
+
 
+func fire():
+	print('fired!')
+	var p = Projectile.instantiate()
+	p.spawn(owner, projectile_effects, transform)
 
 # Called every frame. 'delta' is the elapsed time since the previous frame.
 func _physics_process(delta):
@@ -32,9 +47,5 @@ func _physics_process(delta):
 		position.x += HORIZONTAL_SPEED * delta
 
 	if Input.is_action_just_pressed("fire"):
-		print('fired!')
-		var p = Projectile.instantiate()
-		p.spawn(owner, projectile_effects)
-		# TODO:: This transform should probably be modifiable by projectile effects too?
-		p.transform = projectile_spawner.global_transform
+		fire()
 

units/projectile.gd

@@ -4,16 +4,18 @@ const SPEED = 750
 var projectile_effects: Array[ProjectileEffect] = []
 
 
-func spawn(owner: Node, spawn_with_projectile_effects: Array[ProjectileEffect]):
+func spawn(owner: Node, spawn_with_projectile_effects: Array[ProjectileEffect], parent_transform: Transform2D):
 	# Execute any spawn modification effects for the projectile
+	print("spawned!")
 	projectile_effects = spawn_with_projectile_effects
 	for effect in projectile_effects:
-		effect.modify_creation(owner)
+		effect.modify_creation(owner, projectile_effects, parent_transform)
 	# Spawn the default projectile
 	# TODO:: Projectile spawn modification may want to prevent the default from spawning
 	#    how do?
 	owner.add_child(self)
 	projectile_effects = projectile_effects
+	transform = parent_transform
 
 func _physics_process(delta):
 	var position_modifier = transform.x * SPEED * delta