selection box for top-down 2D game in Godot

selectionBox.gd

extends Control

var initialPos
var currentPos

func _ready(true):
  set_process(true)

func _process(delta):
  createBox()

func createBox():
	if Input.is_action_pressed("ui_left_mouse_button"):
		initialPos = get_global_mouse_position()
		rectd.set_begin(initialPos)
	if Input.is_action_pressed("ui_left_mouse_button"):
		currentPos = get_global_mouse_position()
		rectd.set_begin(Vector2(min(initialPos.x, currentPos.x), min(initialPos.y, currentPos.y)))
		rectd.set_end(Vector2(max(initialPos.x, currentPos.x), max(initialPos.y, currentPos.y)))
	if Input.is_action_just_released("ui_left_mouse_button"):
		rectd.set_begin(Vector2(0, 0))
		rectd.set_end(Vector2(0, 0))