private bool powerUp = false;

    void Update()
    {
        Fire();
    }

    private void Fire()
    {
        if(powerUp == false)
        {
            if (Input.GetButtonDown("Fire1"))
            {
                firingCoroutine = StartCoroutine(FireContiuously());
            }

            if (Input.GetButtonUp("Fire1"))
            {
                StopCoroutine(firingCoroutine);
            }
        }
        else
        {
            if (Input.GetButtonDown("Fire1"))
            {
                firingCoroutine1 = StartCoroutine(FireContiuouslyGun1(10f));
                firingCoroutine2 = StartCoroutine(FireContiuouslyGun2(10f));
            }

            //I don't think this is needed!?
            if (Input.GetButtonUp("Fire1"))
            {
                StopCoroutine(firingCoroutine1);
                StopCoroutine(firingCoroutine2);

                //Unless you set the powerUp to false, because you might get infinite powerup, if my logic is correct, which probably isn't.
                //powerUp = false;
            }
        }

        //vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
        //If you want to combine the normal firing with the powerup, use this one
        //vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

        // if (Input.GetButtonDown("Fire1"))
        // {
        //     firingCoroutine = StartCoroutine(FireContiuously());
        // }

        // if (Input.GetButtonUp("Fire1"))
        // {
        //     StopCoroutine(firingCoroutine);
        // }

        // if(powerUp == true)
        // {
        //     if (Input.GetButtonDown("Fire1"))
        //     {
        //         firingCoroutine1 = StartCoroutine(FireContiuouslyGun1(10f));
        //         firingCoroutine2 = StartCoroutine(FireContiuouslyGun2(10f));
        //     }

        //     if (Input.GetButtonUp("Fire1"))
        //     {
        //         StopCoroutine(firingCoroutine1);
        //         StopCoroutine(firingCoroutine2);
        //
        //         powerUp = false;
        //     }
        // }
    }

    IEnumerator FireContiuously()
    {
        while (true)
        {
            GameObject bullet = Instantiate(projectile, transform.position, Quaternion.identity) as GameObject;

            bullet.GetComponent<Rigidbody2D>().velocity = new Vector2(0, projectileSpeed);
            sfx.GetShootSFX();

            yield return new WaitForSeconds(firingPeriod);
        }

    }

    public void OnTriggerEnter2D(Collider2D doubleBullets)
    {
        if(doubleBullets.gameObject.CompareTag("Double Bullets"))
        {
            Destroy(doubleBullets.gameObject);
            StopCoroutine(FireContiuously() /* <- Isn't this suppose to be firingCoroutine? */ );

            powerUp = true;
        }
    }

    IEnumerator FireContiuouslyGun1(float timeLimit)
    {
        while (timeLimit > 0f)
        {
            timeLimit -= firingPeriod;

            GameObject bullet = Instantiate(projectile, gun1.transform.position, Quaternion.identity) as GameObject;

            bullet.GetComponent<Rigidbody2D>().velocity = new Vector2(0, projectileSpeed);
            sfx.GetShootSFX();

            yield return new WaitForSeconds(firingPeriod); //Changed to firingPeriod
        }

        powerUp = false;
    }

    IEnumerator FireContiuouslyGun2(float timeLimit)
    {
        while (timeLimit > 0f)
        {
            timeLimit -= firingPeriod;

            GameObject bullet = Instantiate(projectile, gun2.transform.position, Quaternion.identity) as GameObject;

            bullet.GetComponent<Rigidbody2D>().velocity = new Vector2(0, projectileSpeed);
            sfx.GetShootSFX();

            yield return new WaitForSeconds(firingPeriod); //Changed to firingPeriod
        }

        powerUp = false;
    }