How do I modify my script to give my gun recoil when I shoot?

you could make me a new script or modify the shoot script here if you want. Here is my script:

     var projectile : Rigidbody;
     var speed = 20;
     var cloneSpeed = 10;
     function Update () {
     
     if ( Input.GetButtonDown ("Fire1")) {
     
     clone = Instantiate(projectile, transform.position, transform.rotation);
     clone.velocity = transform.TransformDirection( Vector3 (1, 1, speed));
     
     Destroy (clone.gameObject, 5);
     
     }}