Y Axis fpsshooter fallow

I am working on a fps, and i can get it to shoot, and to fallow the mouse side to side, but it will only shoot at a fixed height. i want it to shoot on the Y axis too.
please help!
(this is the script I’m using to shoot)

  
var projectile : Rigidbody; 
var speed = 20;

    function Update()
    {
        if( Input.GetButton( "Fire1" ) )
        {
            var instantiatedProjectile : Rigidbody = Instantiate(
        projectile, transform.position, transform.rotation );

            instantiatedProjectile.velocity =
        transform.TransformDirection( Vector3( 0, 0, speed ) );

            Physics.IgnoreCollision( instantiatedProjectile. collider,
        transform.root.collider );
    }
}

Well, instead of using the player’s transform, why not just use the camera’s?

Everywhere where you use ‘transform’, instead use ‘Camera.main.transform’!