GameData Script

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.IO;
using UnityEngine.SceneManagement;
using System.Runtime.CompilerServices;

[System.Serializable]
public class HighScoreData
{
    public int highscore1P;
    public int highscore2P;
}

[System.Serializable]
public class CurrencyData
{
    public int LifeEssence;
}

[System.Serializable]
public class ShopData
{
    public int HealthCost;
}

[System.Serializable]
public class PlayerData
{
    public int HealthAmount;
}

public class GameData : MonoBehaviour
{
    public static GameData instance;

    public HighScoreData highScoreData;
    public CurrencyData currencyData;
    public ShopData shopData;
    public PlayerData playerData;

    void Awake()
    {
        if (instance == null)
        {
            instance = this;
            DontDestroyOnLoad(gameObject);

            if (!PlayerPrefs.HasKey("FirstEverStartedGame"))
            {
                PlayerPrefs.SetInt("FirstEverStartedGame", 1);

                currencyData.LifeEssence = 0;
                shopData.HealthCost = 1;
                playerData.HealthAmount = 4;

                SaveCurrency(currencyData.LifeEssence);
                SaveShopData(shopData.HealthCost);
                SavePlayerData(playerData.HealthAmount);
            }

            LoadHighScore();
            LoadCurrency();
            LoadShopData();
            LoadPlayerData();
        }
        else
        {
            Destroy(gameObject);
        }
    }

    public void SaveHighScore(int newHighScore)
    {
        Scene currentScene = SceneManager.GetActiveScene();

        string sceneName = currentScene.name;

        if (sceneName == "MainGame1P")
        {
            highScoreData.highscore1P = newHighScore;
            string jsonData = JsonUtility.ToJson(highScoreData);
            File.WriteAllText("HighscoreData.json", jsonData);
        }
        else if (sceneName == "MainGame2P")
        {
            highScoreData.highscore2P = newHighScore;
            string jsonData = JsonUtility.ToJson(highScoreData);
            File.WriteAllText("HighscoreData.json", jsonData);
        }
    }

    void LoadHighScore()
    {
        if (File.Exists("HighscoreData.json"))
        {
            string jsonData = File.ReadAllText("HighscoreData.json");
            highScoreData = JsonUtility.FromJson<HighScoreData>(jsonData);
        }
    }

    public void SaveCurrency(int newLifeEssence)
    {
        currencyData.LifeEssence = newLifeEssence;
        string jsonData = JsonUtility.ToJson(currencyData);
        File.WriteAllText("CurrencyData.json", jsonData);
    }

    void LoadCurrency()
    {
        if (File.Exists("CurrencyData.json"))
        {
            string jsonData = File.ReadAllText("CurrencyData.json");
            currencyData = JsonUtility.FromJson<CurrencyData>(jsonData);
        }
    }

    public void SaveShopData(int newHealthCost)
    {
        shopData.HealthCost = newHealthCost;
        string jsonData = JsonUtility.ToJson(shopData);
        File.WriteAllText("ShopData.json", jsonData);
    }

    void LoadShopData()
    {
        if (File.Exists("ShopData.json"))
        {
            string jsonData = File.ReadAllText("ShopData.json");
            shopData = JsonUtility.FromJson<ShopData>(jsonData);
        }
    }

    public void SavePlayerData(int newHealthAmount)
    {
        playerData.HealthAmount = newHealthAmount;
        string jsonData = JsonUtility.ToJson(playerData);
        File.WriteAllText("PlayerData.json", jsonData);
    }

    void LoadPlayerData()
    {
        if (File.Exists("PlayerData.json"))
        {
            string jsonData = File.ReadAllText("PlayerData.json");
            playerData = JsonUtility.FromJson<PlayerData>(jsonData);
        }
    }
}