GDScript in Godot 4 @onready var Explained

main.gd

extends Node2D

const MAX_HEALTH = 5
var health = MAX_HEALTH
@onready var health_bar = $HealthBar
@onready var health_label = $HealthLabel

func _ready() -> void:
  update_health_ui()
  health_bar.max_value = MAX_HEALTH

func update_health_ui():
  set_health_label()
  set_health_bar()

func set_health_label() -> void:
  health_label.text = "Health: %s" % health

func set_health_bar() -> void:
  health_bar.value = health

func _input(event: InputEvent) -> void:
  if event.is_action_pressed("ui_accept"):
    damage()

func damage() -> void:
  health -= 1
  if health < 0:
    health = MAX_HEALTH
  update_health_ui()