feat: add plasma gun weapon implementation and new pause menu system with loadout management

weapons/projectile.gd

@@ -0,0 +1,59 @@
+extends Node3D
+class_name Projectile
+
+var velocity: Vector3 = Vector3.ZERO
+var damage: float = 10.0
+var max_range: float = 200.0
+var distance_traveled: float = 0.0
+var owner_player: CharacterBody3D
+var falloff_start: float = 10.0
+var min_damage: float = 5.0
+var drop_gravity: float = 0.0 # For arc projectiles (nailgun might have slight drop, plasma none)
+
+var _previous_position: Vector3
+
+func _ready() -> void:
+	_previous_position = global_position
+	# Automatically destroy after 5 seconds to prevent leaks
+	var t = get_tree().create_timer(5.0)
+	t.timeout.connect(queue_free)
+
+func _physics_process(delta: float) -> void:
+	# Apply gravity drop if any
+	velocity.y -= drop_gravity * delta
+	
+	var movement = velocity * delta
+	global_position += movement
+	
+	distance_traveled += movement.length()
+	
+	if distance_traveled > max_range:
+		queue_free()
+		return
+		
+	_check_collision()
+	_previous_position = global_position
+
+func _check_collision() -> void:
+	var space_state = get_world_3d().direct_space_state
+	var query = PhysicsRayQueryParameters3D.create(_previous_position, global_position)
+	if owner_player:
+		query.exclude = [owner_player.get_rid()]
+		
+	var result = space_state.intersect_ray(query)
+	if result:
+		_on_hit(result)
+		
+func _on_hit(result: Dictionary) -> void:
+	var hit_dist = distance_traveled - (_previous_position.distance_to(result.position))
+	
+	var final_damage = damage
+	if hit_dist > falloff_start and falloff_start > 0.0:
+		var falloff_factor = clampf((hit_dist - falloff_start) / (max_range - falloff_start), 0.0, 1.0)
+		final_damage = lerpf(damage, min_damage, falloff_factor)
+		
+	if result.collider.has_method("take_damage"):
+		result.collider.take_damage(final_damage, result.position, owner_player)
+		
+	# Spawn impact effect? Not needed yet for prototype.
+	queue_free()