【Unity】Sceneを読みんだあとに、ゲームが開始しない

C#
1using System.Collections;
2using System.Collections.Generic;
3using UnityEngine;
4using UnityEngine.SceneManagement;
5using UnityEngine.UI;
6
7public class GamePlayScripts : MonoBehaviour
8{
9    public GameObject gameOverPanel;
10
11    public ParticleSystem muzzleFlashPar;   
12
13
14    AudioSource gunShotAudioSource;
15    public AudioClip gunShotClip;
16
17    public GameObject timerTextView;
18
19    public GameObject scoreTextView;
20    int roundsShot = 0;
21    int enemyKilled = 0;
22
23
24    public GameObject bazookaGo;
25    public GameObject crossHairGo;
26
27    bool gameIsPaused = false;
28
29
30    int gameTime = 3;         //ゲーム開始時のタイム
31
32
33
34	// Use this for initialization
35	void Start () {
36
37        scoreTextView.GetComponent<Text>().text = enemyKilled.ToString() + " / " + roundsShot.ToString();
38
39
40
41        gunShotAudioSource = gameObject.GetComponent<AudioSource>();
42        InvokeRepeating("timeCounterAction", 0, 1);     //何度も繰りかえす
43		
44	}
45
46    int timeMinutes;
47    int timeSecond;
48
49    void timeCounterAction ()
50    {
51        if(gameTime > 0)
52        { 
53
54        timeMinutes =(int) (gameTime / 60);     //分
55        timeSecond = gameTime % 60;             //秒
56
57        string timerTextString = timeMinutes.ToString("D1") + "\' " + timeSecond.ToString("D2") + "\"";
58        timerTextView.GetComponent<Text>().text = timerTextString;  //int型を文字型に変える
59        gameTime = gameTime - 1;    //秒数を減らす
60        }
61        else
62        {
63            Time.timeScale = 0;
64            gameIsPaused = true;
65            gameOverPanel.GetComponent<CanvasGroup>().alpha = 1;
66            gameOverPanel.GetComponent<CanvasGroup>().interactable = true;
67            gameOverPanel.GetComponent<CanvasGroup>().blocksRaycasts = true;
68        }
69    }
70
71
72    void shootAction()
73    {
74        gunShotAudioSource.PlayOneShot(gunShotClip);
75        muzzleFlashPar.Emit(1);
76
77        roundsShot++;
78        
79
80        Vector2 dir = new Vector2(crossHairGo.transform.position.x, crossHairGo.transform.position.y);
81        RaycastHit2D hit = Physics2D.Raycast(Camera.main.transform.position, dir);
82
83
84        if(hit.collider != null && hit.collider.gameObject != crossHairGo)
85        {
86            enemyKilled++;
87            Destroy(hit.collider.gameObject);
88        }
89
90        scoreTextView.GetComponent<Text>().text = enemyKilled.ToString() + " / " + roundsShot.ToString();
91
92    }
93	
94	// Update is called once per framec
95	void Update ()
96    {
97            if (!gameIsPaused)
98        {
99
100            if (Input.GetKeyUp(KeyCode.Space))
101             shootAction();
102            
103
104            bazookaGo.transform.LookAt(crossHairGo.transform);
105
106            float h = Input.GetAxis("Mouse X") / 5;
107            float v = Input.GetAxis("Mouse Y") / 5;
108
109            Vector3 crossHairMov = new Vector3(h, v, 0);
110            crossHairGo.transform.Translate(crossHairMov);
111
112            float x = crossHairGo.transform.position.x;
113            float y = crossHairGo.transform.position.y;
114
115            if (x > 10)
116                x = 10;
117            if (x < -10)
118                x = -10;
119
120            if (y > 6)
121                y = 6;
122            if (y < -6)
123                y = -6;
124
125            crossHairGo.transform.position = new Vector3(x, y, 0);
126
127        }
128
129    }
130
131    public void OnRetry()
132    {
133        SceneManager.LoadScene("GamePlay Scene");
134    }
135}
136このようなコードを書いて、クリック時にGamePlay Sceneを読み込むことができるようになりました。しかし、ゲームがスタートしません。
137
138どのようにしたら、ゲームがスタートしますか？
139