ProjectileController.cs

using UnityEngine;
using System.Collections;

public class ProjectileController : MonoBehaviour {

    public float speed;

    public mario player;


    public LevelManager levelManager;
    public LevelManager2 levelManager2;

    // Use this for initialization
    void Start () {
        player = FindObjectOfType<mario>();

        if (player.GetComponent<Rigidbody2D>().velocity.x < 0)
            speed = -speed;

        levelManager = FindObjectOfType<LevelManager>();
        levelManager2 = FindObjectOfType<LevelManager2>();

    }
	                                                                  
	// Update is called once per frame
	void Update () {
        GetComponent<Rigidbody2D>().velocity = new Vector2(speed, GetComponent<Rigidbody2D>().velocity.y);

	}

    void OnTriggerEnter2D(Collider2D other)
    {
        if (other.name == "mario")
        {
            levelManager.RespawnPlayer();
        }
        if (other.name == "mario2")
        {
            levelManager2.RespawnPlayer();
        }
        Destroy (gameObject);
    }
}