Arcade Shooter GameController

using UnityEngine;
using System.Collections;

public class GameController : MonoBehaviour {

    public GameObject enemy;
    public int enemyCount; // 10

    private int score;

    private bool gameOver;
    private bool restart;

    void Awake () {
        score = 0;
        gameOver = false;
        restart = false;
    }

    void Start () {
        StartCoroutine(SpawnWaves ());
    }

    void OnGUI () {
        GUI.Label(new Rect(10, 10, 100, 20), "Score: " + score);
        if (gameOver) {
            GUI.Label(new Rect(Screen.width / 2 - 40, Screen.height / 3, 80, 20), "Game Over!");
        }
        if (restart) {
            if (GUI.Button(new Rect(Screen.width - 70, 10, 60, 20), "Restart")) {
                Application.LoadLevel(Application.loadedLevel);
            }
        }
    }

    IEnumerator SpawnWaves () {
        yield return new WaitForSeconds (1.0f);

        while (true) {
            for (int i = 0; i < enemyCount; i++) {
                Vector3 spawnPosition = new Vector3(Random.Range(-9.0f, 9.0f), 0.0f, 26.0f);
                GameObject clone = Instantiate(enemy, spawnPosition, Quaternion.identity) as GameObject;
                clone.transform.parent = transform;
                yield return new WaitForSeconds (0.5f);
            }

            yield return new WaitForSeconds (3.0f);

            if (gameOver) {
                restart = true;
                break;
            }
        }
    }

    public void AddScore (int newScoreValue) {
        score += newScoreValue;
    }

    public void GameOver () {
        gameOver = true;
    }
}