RatAttack2D/Assets/PauseMenu.cs

using UnityEngine;
using System.Collections;
using UnityEngine.InputSystem;

public class PauseMenu : MonoBehaviour
{

    public GameObject pauseMenu;
    private bool paused = false;

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.Escape))
        {
            paused = !paused;
        }
        if (paused)
        {
            pauseMenu.SetActive(true);
            Time.timeScale = 0;
        }
        else
        {
            pauseMenu.SetActive(false);
            Time.timeScale = 1;
        }
    }
}