Drill 1: Find the core line — Saving and loading

using System.IO;
using UnityEngine;

[System.Serializable]
public class SaveData
{
    public int score;
    public float version = 1f;
}

public class SaveSystem : MonoBehaviour
{
    private string SavePath => Path.Combine(Application.persistentDataPath, "save.json");

    public void Save(SaveData data)
    {
        string json = JsonUtility.ToJson(data);
        File.WriteAllText(SavePath, json);
    }

    public SaveData Load()
    {
        if (!File.Exists(SavePath)) return new SaveData();
        string json = File.ReadAllText(SavePath);
        return JsonUtility.FromJson<SaveData>(json);
    }
}