Platformer Movement

extends Node2D

func _ready() -> void:
	# "_ready()" runs once, when the scene starts. Setup goes here.
	# GoalArea is the green zone at the top of the level. We put the name
	# "_on_goal_reached" inside ".connect()". That is the function Godot
	# runs when something touches it.
	%GoalArea.body_entered.connect(_on_goal_reached)

# "body" is whatever touched the goal zone.
func _on_goal_reached(body: Node2D) -> void:
	# "PlatformPlayer" is the class_name at the top of player.gd.
	if body is PlatformPlayer:
		# hud.gd connects to "goal_reached" and puts the win message on screen.
		GameEvents.goal_reached.emit()

extends CanvasLayer

# "%MessageLabel" means "the node named MessageLabel in this scene."
@onready var message_label: Label = %MessageLabel

func _ready() -> void:
	# platformer_movement.gd emits "goal_reached" when the player touches the
	# green zone. We put "_on_goal_reached" inside ".connect()". That is the
	# function Godot runs when the signal arrives.
	GameEvents.goal_reached.connect(_on_goal_reached)
	%HomeButton.pressed.connect(_on_home_pressed)

# Loads the lesson list screen, which replaces this whole scene.
func _on_home_pressed() -> void:
	get_tree().change_scene_to_file("res://shared/ui/lesson_select.tscn")

func _on_goal_reached() -> void:
	message_label.text = "You reached the top!"

class_name PlatformPlayer
extends CharacterBody2D

## How fast the player runs left and right.
@export var speed: float = 200.0
## How hard the player jumps. This number is NEGATIVE on purpose. In Godot
## the top of the screen is 0 and the numbers grow going down, so up is
## the negative direction.
@export var jump_velocity: float = -650.0
## How hard gravity pulls down. A bigger number means you fall faster.
@export var gravity: float = 1800.0

# This one function does four jobs. Here they are, one at a time.
func _physics_process(delta: float) -> void:
	# STEP 1: FALL. If our feet are not on the ground, gravity pulls us
	# down. Notice it is "+=" and not "=": we add a little more speed every
	# frame, so the longer you fall the faster you drop.
	if not is_on_floor():
		velocity.y += gravity * delta

	# STEP 2: JUMP. "is_action_just_pressed" is true only on the one frame
	# the key goes down. (If we used "is_action_pressed" it would be true
	# the whole time you hold the key, and you would jump over and over.)
	# The "is_on_floor()" check is what stops you jumping in mid-air.
	if Input.is_action_just_pressed("jump") and is_on_floor():
		velocity.y = jump_velocity

	# STEP 3: RUN. "get_axis()" hands back a single number:
	#   -1 for left, 1 for right, and 0 for neither.
	var direction: float = Input.get_axis("move_left", "move_right")
	velocity.x = direction * speed

	# STEP 4: MOVE. Steps 1 to 3 only DECIDED where to go.
	# "move_and_slide()" is the line that actually moves us.
	move_and_slide()

	# The warrior picture only faces right. Walking left mirrors it.
	if direction != 0.0:
		$Sprite2D.flip_h = direction < 0.0