5.3 — Into the Cave: Scenes, Persistence & The Refactor

Compare against your own file rather than copying it. Three things have to match: the fields are gone from PlayerController rather than copied, the duplicate branch is really there — this project loads a second StatManager the moment you walk back into Start (index 0) — and your own damage and death rules came across from 2.2 and 2.3 exactly as you wrote them. The accessor names — Instance, GetCoins, GetHealth, GetMaxHealth, HasAxe, AddCoins, TakeDamage, SetHasAxe — are the ones the HUD calls.

// ------------------------------------------------------------------
//  REFERENCE FILE — Assets/Scripts/StatManager.cs
//  Written to be read, not pasted. Build it with the walkthrough
//  above, one step at a time, then open this and compare.
//  If it is sitting in your project unchanged, that is the thing
//  to go and do now — the walkthrough is still above you.
// ------------------------------------------------------------------
using UnityEngine;

// StatManager.cs — the numbers the player earned, on the one object a scene
// load is not allowed to destroy.
public class StatManager : MonoBehaviour
{
    public static StatManager Instance;

    [SerializeField] private int coins;
    [SerializeField] private int health = 3;
    [SerializeField] private int maxHealth = 3;
    [SerializeField] private bool hasAxe;

    private void Awake()
    {
        // Somebody is already alive. This copy is the one that leaves — the
        // Start scene has its own manager object, and you can walk back to it.
        if (Instance != null && Instance != this)
        {
            Destroy(gameObject);
            return;
        }

        Instance = this;
        DontDestroyOnLoad(gameObject);
    }

    public int GetCoins() { return coins; }
    public int GetHealth() { return health; }
    public int GetMaxHealth() { return maxHealth; }
    public bool HasAxe() { return hasAxe; }

    public void AddCoins(int amount)
    {
        coins = coins + amount;
    }

    // One method, one signed amount: the spike calls it positive, the potion
    // calls it negative. Same name and signature as the one on the player, so
    // every existing caller changes its receiver and nothing else.
    public void TakeDamage(int amount)
    {
        health = health - amount;

        // The ceiling from 2.3, on the only object that holds the value it
        // protects. No caller can get above it.
        health = Mathf.Clamp(health, 0, maxHealth);
        Debug.Log("Health: " + health);

        // ...and YOUR death rule from 2.2 goes here: the "already at zero"
        // guard at the top of the method, and whatever should happen when
        // health reaches zero. Moved across, not rewritten.
    }

    public void SetHasAxe(bool value)
    {
        hasAxe = value;
    }
}

// Callers, in PlayerController.cs — the receivers changed, nothing else:
//   StatManager.Instance.TakeDamage(1);      <- the spike branch (2.2)
//   StatManager.Instance.AddCoins(1);        <- the coin branch (2.1)
//   StatManager.Instance.SetHasAxe(true);    <- the axe branch (5.1)
// ...and in the projectile from 3.4, which no longer needs a reference to the
// player at all: StatManager.Instance.TakeDamage(damage);

Compare against your own file rather than copying it. Three things to check: the using TMPro; line is there, the string is built inside Update() rather than once in Start(), and every value is read from StatManager.Instance rather than from the player. The walkthrough builds that string in one expression and appends the axe line where this file assigns it in an if/else; both write the same characters to the same property. Your label text, your placement and what you choose to display are yours — the shape is the slot, the guard, and the rebuild in Update().

// ------------------------------------------------------------------
//  REFERENCE FILE — Assets/Scripts/HudController.cs
//  Written to be read, not pasted. Build it with the walkthrough
//  above, one step at a time, then open this and compare.
//  If it is sitting in your project unchanged, that is the thing
//  to go and do now — the walkthrough is still above you.
// ------------------------------------------------------------------
using UnityEngine;
using TMPro;

// HudController.cs — the numbers, on screen. It owns no state at all: every
// value is read from the manager each frame and thrown away again.
public class HudController : MonoBehaviour
{
    [SerializeField] private TextMeshProUGUI statsText;

    void Update()
    {
        // No manager in this scene (you pressed Play in the Overworld)? There
        // is nothing to show and nothing to crash over.
        if (StatManager.Instance == null)
        {
            return;
        }

        int coins = StatManager.Instance.GetCoins();
        int health = StatManager.Instance.GetHealth();
        int maxHealth = StatManager.Instance.GetMaxHealth();

        string line;

        if (StatManager.Instance.HasAxe())
        {
            line = "Coins: " + coins + "   Health: " + health + " / " + maxHealth + "   Axe: yes";
        }
        else
        {
            line = "Coins: " + coins + "   Health: " + health + " / " + maxHealth;
        }

        statsText.text = line;

        // If reading every frame ever shows up as a cost, the fix is not to
        // stop reading. Remember the last values and rebuild the string only
        // when one of them changes.
    }
}