Character movement problem

 public class Movement : MonoBehaviour {
     public float speed = 6.0F;
     public float jumpSpeed = 8.0F;
     public float gravity = 20.0F;
     private Vector3 moveDirection = Vector3.zero;
     public float speedi;
     void Update() {
         CharacterController controller = GetComponent<CharacterController>();
         if (controller.isGrounded) {
             moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
             moveDirection = transform.TransformDirection(moveDirection);
             moveDirection *= speed;
             if (Input.GetButton("Jump"))
                 moveDirection.y = jumpSpeed;
             
         }
         moveDirection.y -= gravity * Time.deltaTime;
         controller.Move(moveDirection * Time.deltaTime);
     }
     void FixedUpdate () 
     {
         // Generate a plane that intersects the transform's position with an upwards normal.
         Plane playerPlane = new Plane(Vector3.up, transform.position);
  
         // Generate a ray from the cursor position
         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
  
         // Determine the point where the cursor ray intersects the plane.
         // This will be the point that the object must look towards to be looking at the mouse.
         // Raycasting to a Plane object only gives us a distance, so we'll have to take the distance,
         //   then find the point along that ray that meets that distance.  This will be the point
         //   to look at.
         float hitdist = 0.0f;
         // If the ray is parallel to the plane, Raycast will return false.
         if (playerPlane.Raycast (ray, out hitdist)) 
         {
             // Get the point along the ray that hits the calculated distance.
             Vector3 targetPoint = ray.GetPoint(hitdist);
  
             // Determine the target rotation.  This is the rotation if the transform looks at the target point.
             Quaternion targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
  
             // Smoothly rotate towards the target point.
             transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, speedi * Time.time);
         }
     }
 }

problem is the object move towards the mouse position . but ı want it to move globally independent to the mouse position.