Boundries.cs

using UnityEngine;
using System.Collections;

public class Boundries : MonoBehaviour
{
    void OnCollisionEnter(Collision collision)
    {
        if (collision.gameObject.CompareTag("EnemyBullet"))
        {
            Destroy(collision.gameObject);

        }

        if (collision.gameObject.CompareTag("Enemy"))
        {
            Destroy(collision.gameObject);

        }
        if (collision.gameObject.CompareTag("Bullet"))
        {
            Destroy(collision.gameObject);

        }
    }
}