RatAttack2D/Assets/SceneSwitcher.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneSwitcher : MonoBehaviour
{
   public void PlayGame()
    {
         SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex + 1);
    }
    public void Back()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex - 1);
    }
}