Godot for kids and teens

# player.gd on an Area2D (ours: the Dodge the Creeps!
# player, shortened with Input.get_vector)
extends Area2D

signal hit

@export var speed = 400  # pixels per second
var screen_size

func _ready():
    screen_size = get_viewport_rect().size

func _process(delta):
    var direction = Input.get_vector("move_left", "move_right", "move_up", "move_down")
    position += direction * speed * delta
    position = position.clamp(Vector2.ZERO, screen_size)

func _on_body_entered(_body):
    hide()
    hit.emit()
    $CollisionShape2D.set_deferred("disabled", true)

Map move_left, move_right, move_up and move_down in Project Settings, Input Map, as the lesson describes. The Input class reference says get_vector gives a vector whose length is limited to 1. The official lesson reaches the same result with four if statements and normalized(), and explains the reason: holding right and down at the same time makes the vector (1, 1). Our arithmetic: the length of (1, 1) is about 1.41, so with no limit a diagonal runner at speed 400 would cover about 566 pixels a second instead of 400, roughly 41 percent faster.

# main.gd on a Node with two children: a Timer
# and a Label named ScoreLabel (ours)
extends Node

var score = 0

func _ready():
    var timer = get_node("Timer")
    timer.timeout.connect(_on_timer_timeout)
    timer.start()

func _on_timer_timeout():
    score += 1
    $ScoreLabel.text = str(score)

Set the Timer’s Wait Time to 1 in the Inspector, the value the docs use for the score timer in Dodge the Creeps!. The signals lesson connects a timer with the same line, timer.timeout.connect(_on_timer_timeout).