CHALLENGE 3: Coins Worth Different Amounts
====================================================================

TASK
----
Give each Coin a random chance (e.g. 20%) of being a "big coin"
worth 50 points instead of 10, decided once when it's instanced in
main.gd. Have the coin's own coin_collected signal pass its point
value as an argument so _on_coin_collected can add the correct
amount.

SOLUTION CODE - the updated coin.gd
-----------------------------------------
extends Area2D

signal coin_collected(points: int)

var point_value: int = 10

func _ready() -> void:
    body_entered.connect(_on_body_entered)

func _on_body_entered(body: Node2D) -> void:
    if body.is_in_group("player"):
        $CollisionShape2D.set_deferred("disabled", true)
        $Sprite2D.hide()
        coin_collected.emit(point_value)
        $AudioStreamPlayer2D.play()
        await $AudioStreamPlayer2D.finished
        queue_free()

SOLUTION CODE - the updated parts of main.gd
---------------------------------------------------
func _ready() -> void:
    $Player/Health.died.connect(_on_player_died)

    for pos in COIN_POSITIONS:
        var coin = CoinScene.instantiate()
        $CoinSpawner.add_child(coin)
        coin.position = pos

        if randf() < 0.2:
            coin.point_value = 50
            coin.get_node("Sprite2D").modulate = Color(1.0, 0.85, 0.2)  # tint it gold

        coin.coin_collected.connect(_on_coin_collected)
        coins_remaining += 1

func _on_coin_collected(points: int) -> void:
    score += points
    coins_remaining -= 1
    $HUD/ScoreLabel.text = "Score: " + str(score)

    if coins_remaining == 0:
        $WinParticles.restart()
        print("You collected every coin - you win!")

WHY THIS WORKS AS AN ANSWER
----------------------------
coin.gd's own point_value is a plain public variable, defaulting to
10 - since it's set directly on the Coin instance right after
instantiate() and before add_child() (or immediately after, as
shown), each Coin can carry its own independent value without coin.gd
needing to know anything about randomness or probability itself; it
just emits whatever point_value happens to already be.

Deciding "is this a big coin?" in main.gd, right where each coin is
spawned, keeps that randomness in exactly one place rather than
duplicated inside coin.gd - matching the chapter's own principle that
main.gd is the one script that's allowed to know detailed things
about how the game as a whole is configured, while Coin itself stays
a simple, reusable, self-contained piece.

Changing the signal to coin_collected(points: int) means
_on_coin_collected now receives the exact point value of whichever
coin was just collected, rather than a hardcoded 10 - so score += 10
becomes score += points, correctly adding 50 for a big coin and 10
for a regular one, with no separate lookup or coin-type check needed
in main.gd at all; the coin already tells you exactly what it's
worth.