Unity 5 Player Movement

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(CharacterController))]
public class PlayerMovement : MonoBehaviour {

    private CharacterController charCtrl;
    private Vector3 moveDirection = Vector3.zero;
    private bool hasJumped = false;

    public float MoveSpeed = 6f;
    public float JumpSpeed = 20f;
    public float Gravity = 2f;

    void Start() {
        charCtrl = GetComponent<CharacterController>();
    }

    void Update() {
        if (charCtrl.isGrounded) {
            moveDirection.x = Input.GetAxisRaw("Horizontal");
            moveDirection.y = 0f;
            moveDirection.z = Input.GetAxisRaw("Vertical");
            moveDirection = transform.TransformDirection(moveDirection);
            moveDirection.Normalize();
            moveDirection *= MoveSpeed;
            if (Input.GetButton("Jump")) {
                if (!hasJumped) {
                    hasJumped = true;
                    moveDirection.y = JumpSpeed;
                }
            } else if (hasJumped) {
                hasJumped = false;
            }
        }
        moveDirection.y += Gravity;
        charCtrl.Move(moveDirection * Time.deltaTime);
    }

}