GameScecneManager Code

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

public class GameSceneManager : MonoBehaviour
{

    float ballIntervalMax = 2.0f;
    float ballIntervalMin = 0.2f;
    float timeToMinimumInterval = 30.0f;
    public float gameTime;

    public Camera mainCamera;
    public Text  scoreText;
    public Text gameOverText;
    public PlayerController player;
    public GameObject ballPrefab;

    Vector3 leftBound;
    int score = 0;
    float gameTimer;
    float ballTimer;
    bool gameOver = false;

    void Start()
    {
        Time.timeScale = 1;
        ballTimer = ballIntervalMax;

        leftBound = mainCamera.ViewportToWorldPoint(new Vector3(0,1, -mainCamera.transform.localPosition.z));

        player.OnCollectBall += OnCollectBall;

    }


    void Update()
    {
        gameOverLogic();
        printScoreText();
        setUpTimers();
    }

    void gameOverLogic()
    {
        if(gameOver)
        {
            if(Input.GetKeyDown("r"))
            {
                SceneManager.LoadScene(SceneManager.GetActiveScene().name);
            }

            scoreText.enabled = false;
            gameOverText.enabled = true;


            gameOverText.text = "Game Over Total Score: " + score + "\nPress R to Restart!";

            return;
        }
    }

    void printScoreText()
    {
        scoreText.text = "Score: " + score + "\nTime Left: " + Mathf.Floor(Mathf.Max((gameTime - gameTimer), 0));
    }
    void setUpTimers()
    {
        gameTimer += Time.deltaTime;
        ballTimer -= Time.deltaTime;
        if (ballTimer <= 0)
        {
            float intervalPercentage = Mathf.Min(gameTimer / timeToMinimumInterval, 1);
            ballTimer = ballIntervalMax - (ballIntervalMax - ballIntervalMin) * intervalPercentage;

            GameObject ball = GameObject.Instantiate<GameObject>(ballPrefab);
            ball.transform.SetParent(this.transform);
            ball.transform.position = new Vector3(Random.Range(-5,5), leftBound.y + 2, 0);
        }

    if(gameTimer > gameTime)
    {
        onGameOver();
    }
    }

    public void OnCollectBall()
    {
        if (!gameOver)
        {
            score = score + 100;
        }
    }

    void onGameOver()
    {
        gameOver = true;
        Time.timeScale = 0;
    }

}