Bullet

public class Bullet : MonoBehaviour {

    public float speed;
    public Rigidbody2D rb;
    private Vector2 direction;

    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
    }

    private void FixedUpdate()
    {
        rb.velocity = direction * speed;
    }

    private void OnBecameInvisible()
    {
        Destroy(gameObject);
    }

    public void Initialize(Vector2 direction)
    {
        this.direction = direction;
    }

    public void OnCollisionEnter2D(Collision2D collision)
    {
        if (collision.gameObject.tag.Equals("Enemy"))
        {
            Destroy(gameObject);
            Debug.Log("Bullet has been destroyed");
        }
    }
}