CHALLENGE 1: A Patrolling Hazard
====================================================================

TASK
----
Add a second Hazard that patrols back and forth between two points
using _physics_process and position (Chapter 4's own movement
pattern), rather than sitting still. It should still damage the
player on contact exactly like the first Hazard.

SOLUTION CODE (attached to the second Hazard's Area2D root)
------------------------------------------------------------------
extends Area2D

@export var patrol_distance: float = 150.0
@export var patrol_speed: float = 60.0

var start_x: float
var direction: int = 1

func _ready() -> void:
    start_x = position.x
    body_entered.connect(_on_body_entered)

func _physics_process(delta: float) -> void:
    position.x += direction * patrol_speed * delta

    if position.x > start_x + patrol_distance:
        direction = -1
    elif position.x < start_x - patrol_distance:
        direction = 1

func _on_body_entered(body: Node2D) -> void:
    if body.is_in_group("player"):
        body.get_node("Health").take_damage(20)

WHY THIS WORKS AS AN ANSWER
----------------------------
The damage-on-contact half is completely unchanged from the
capstone's own hazard.gd - body_entered is still connected the same
way, and _on_body_entered still checks the "player" group and calls
take_damage(20) exactly as before. Patrolling and damaging are two
independent responsibilities that don't interfere with each other.

The patrol logic reuses Chapter 4's own delta-scaled movement
pattern (position.x += direction * patrol_speed * delta), just with
a direction that flips between 1 and -1 instead of staying constant.
start_x records the hazard's own starting X position once, in
_ready() - every frame after that, the hazard's current position.x
is compared against start_x + patrol_distance and
start_x - patrol_distance, flipping direction the moment either
boundary is crossed. Because this Hazard is still an Area2D (not a
CharacterBody2D), it moves by directly changing position rather than
using move_and_slide() - which is fine here, since a patrolling
hazard isn't expected to be blocked by walls the way the player is.