The Player doesn't go forward

Hi guys, I have this script but the character go only left, right and backwards... but not forward, why? In the end... the player doesn't jump :(...

 #pragma strict
  
  
 public var Player : GameObject; //Player GameObject
  
 public var Speed : float = 6.0; //Speed
 public var JumpSpeed : float = 8.0; //Jump Speed
 public var Gravity : float = 20.0; //Gravity
  
 public var JumpSound : AudioClip; //Jump Sound
  
 var Health : int = 100; //Health
 var HealthHUD : GUIStyle; //Health GUI
  
 private var moveDirection : Vector3 = Vector3.zero; //Move Direction
  
 function Update() {
  
 var controller : CharacterController = GetComponent(CharacterController);
 if (controller.isGrounded) {
  
 moveDirection = Vector3(Input.GetAxis("Horizontal"), 0,
 Input.GetAxis("Vertical"));
 moveDirection = transform.TransformDirection(moveDirection);
 moveDirection *= Speed;
  
 if(Health == 0)
   {
        Destroy(Player, 0); //Destroy player when health = 0
   }
  
 if (Input.GetButton ("Jump")) { //If the jump key (Space Bar)
 moveDirection.y = JumpSpeed; //Then lift the player in the direction "y."
 audio.PlayOneShot(JumpSound); //Then play the audio clip in "Jump Sound"
    }
 }
  
 // Apply gravity
 moveDirection.y -= Gravity * Time.deltaTime;
  
 // Move the controller
 controller.Move(moveDirection * Time.deltaTime);
 }