boss spawning script problem

Unity Engine
1

hi i currently want to have a boss fight in my game (im taking unity tutorial "Space Shooter"and expanding it)
but i cant get the script to work i have a timer that when it gets to 20 count than spawn the boss but its not doing that heres my script so far:

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class Gameplayer : MonoBehaviour {
    public GameObject[] hazards;
    public GameObject boss;
    public Vector3 spawnval;
    public int hazardcnt;
    public float spawnwait;
    public float startwait;
    public float wavewait;
    public GUIText restarttext;
    public GUIText gameovertxt;
    public GUIText scoreText;
    private int score;
    public float incrementtime = 1f;
    public float incrementby = 1;
    private float counter = 0;
    private bool gameover;
    private bool restart;

    void Start () {
        InvokeRepeating("Increment", incrementtime, incrementby);
if (counter == 10) {
bossfight();
}
        restart = false;
        restarttext.text = "";
        gameovertxt.text = "";
        gameover = false;
        score = 0;
    StartCoroutine    (Spawnstuff ());
        UpdateScore ();
    }
    void Update() {
        if (restart) {
            if (Input.GetKey(KeyCode.R)){
                Application.LoadLevel(Application.loadedLevel);
            }

        }
    }
    IEnumerator Spawnstuff () {
        yield return new WaitForSeconds(startwait);
        while(true) {
        for (int i = 0; i < hazardcnt; i++)
            {
            GameObject hazard = hazards[Random.Range (0, hazards.Length)];
            Vector3 spawnpos = new Vector3 (Random.Range(-spawnval.x, spawnval.x), spawnval.y, spawnval.z);
            Quaternion spawnrot = Quaternion.identity;
            Instantiate (hazard, spawnpos, spawnrot);
            yield return new WaitForSeconds(spawnwait);
            }
            yield return new WaitForSeconds (wavewait);
            if (gameover) {
                restarttext.text = "press 'r' for restart";
                restart = true;
                break;
            }

    }
    }
  
    public void AddScore (int newScoreValue)
    {
        score += newScoreValue;
        UpdateScore ();
    }
  
    void UpdateScore ()
    {
        scoreText.text = "Score: " + score;
    }

    public void GameOver() {
        gameovertxt.text = "Game Over";
        gameover = true;
    }

    void bossfight (){
        Vector3 spawnpos = new Vector3 (spawnval.x, spawnval.y, spawnval.z);
        Quaternion spawnrot = Quaternion.identity;
        Instantiate (boss, spawnpos, spawnrot);
    }

    void Increment () {
        counter += incrementby;
    }
                }
2

your calling the bossfight method in the start function, it wont be called unless the counter is 10 when the game starts.
try putting this somewhere in the update function. and add a boolean to stop it running more than once.

if(counter==20 && !bossSpawned)
{
    bossfight();
    bossSpawned = true;
}