MoveAround js problems

A Sphere in the scene added with a Character Controller componnet. Here is the js I want to control the sphere could be move by keyboards. Here is my code refer to the famous Unity3D tutorial in Youtube.

 var speed: float = 3.0;
 var rotateSpeed: float = 3.0;
 
 
 function Update () 
 { 
     var controller : CharacterController = GetComponent(CharacterController);
  
     transform.Rotate(0, Input.GetAxis ("Horizontal") * rotateSpeed, 0);
  
     var forward : Vector3 = transform.TransformDirection(Vector3.forward);
     var curSpeed : float = speed * Input.GetAxis ("Vertical");
     controller.SimpleMove(forward * curSpeed);
 } 
  
 @script RequireComponent(CharacterController)

Thanks!