public Transform wayPoint;
  public float speed = 10;  
  private bool inForward, inBack;
   
  void Update () {
   if (inForward && Vector3.Distance(transform.position, wayPoint.position) > 1) {
    Vector3 relativePos = wayPoint.position - transform.position;
          Quaternion rotation = Quaternion.LookRotation(relativePos);
          transform.rotation = rotation;
    rigidbody.velocity = transform.forward * Time.deltaTime * speed;
   }
   if (inBack) {
    Vector3 relativePos = wayPoint.position - transform.position;
          Quaternion rotation = Quaternion.LookRotation(relativePos);
          transform.rotation = Quaternion.Inverse(rotation);
    rigidbody.velocity = transform.forward * Time.deltaTime * speed;
   }
  }
   
  void OnGUI () {
   GUILayout.BeginVertical("box");
   if (GUILayout.Button("Forward")) {
    if (inForward == true) {
     inForward = false;
    } else {
     inForward = true;
    }
    inBack = false;
   }
   if (GUILayout.Button("Back")) {
    if (inBack == true) {
     inBack = false;
    } else {
     inBack = true;
    }
    inForward = false;
   }
  }