Area2D not moving (Sources of the First 2D game tutorial)

Greetings!

I'm a very beginner and I'm trying to follow this tutorial: https://docs.godotengine.org/en/stable/getting_started/first_2d_game/03.coding_the_player.html

However my character doesn't move all at, may you help me?

extends Area2D
signal hit

@export var speed = 400 # How fast the player will move (pixels/sec).
var screen_size # Size of the game window.

# Called when the node enters the scene tree for the first time.
func _ready():
	screen_size = get_viewport_rect().size


# Called every frame. 'delta' is the elapsed time since the previous frame.
func _process(delta):
	var velocity = Vector2(Vector2.ZERO)
	
	if Input.is_action_pressed("move_right"):
		velocity.x += 1
	if Input.is_action_pressed("move_left"):
		velocity.x -= 1
	if Input.is_action_pressed("move_down"):
		velocity.y += -1
	if Input.is_action_pressed("move_up"):
		velocity.y -= 1

	if velocity.length() > 0:
		velocity = velocity.normalized() * speed
		$AnimatedSprite2D.play()
	else:
		$AnimatedSprite2D.stop()	
				
	if velocity.x != 0:
		$AnimatedSprite2D.animation = "walk"
		$AnimatedSprite2D.flip_v = false
	# See the note below about boolean assignment.
		$AnimatedSprite2D.flip_h = velocity.x < 0
	elif velocity.y != 0:
		$AnimatedSprite2D.animation = "up"
		$AnimatedSprite2D.flip_v = velocity.y > 0
		
	position += velocity * delta
	position.x = clamp(position.x, 0, screen_size.x)
	position.y = clamp(position.y, 0, screen_size.y)
		
		
func _on_body_entered(_body): 	
	hide() # Player disappears after being hit.
	hit.emit()
	# Must be deferred as we can't change physics properties on a physics callback.
	$CollisionShape2D.set_deferred("disabled", true)
	
	
func start(pos):
	position = pos
	show()
	$CollisionShape2D.disabled = false

Also an image of my project:

Thank you.