enemy waves

    public Transform[] spawn_spots;
    public GameObject enemy;
    public float GameTime, seconds;
    public bool wave_1, wave_2, wave_3 = false;

    void Update()
    {
        seconds = (int)(GameTime % 60f);
        GameTime += Time.deltaTime;

        if (seconds == 5)
        {
            wave_1 = true;
            if (wave_1)
            {
                InvokeRepeating("Spawn", 3.0f, 3.0f);
            }
        }

        if (seconds == 10)
        {
            wave_2 = true;
            wave_1 = false;
            if (wave_2)
            {
                InvokeRepeating("Spawn_2", 5.0f, 5.0f);
            }
        }
    }

    void Spawn()
    {
        int spawnPointIndex = Random.Range(0, spawn_spots.Length);
        Instantiate(enemy, spawn_spots[spawnPointIndex].position, spawn_spots[spawnPointIndex].rotation);
    }

    void Spawn_2()
    {
        int spawnPointIndex = Random.Range(0, spawn_spots.Length);
        Instantiate(enemy, spawn_spots[spawnPointIndex].position, spawn_spots[spawnPointIndex].rotation);
    }