private void Start()
    {
        claw               = GetComponent <AudioSource>();
        agent              = GetComponent <NavMeshAgent>();
        animator           = GetComponent <Animator>();
        dropItemController = GetComponent <DropItemController>();
        player             = FindObjectOfType <PlayerController>().transform;
        healthBar          = GetComponentInChildren <ZombieHealthBar>();

        healthBar.SetSliderValue(currentHealth, maxHealth);

        agent.speed = currentSpeed;
    }
    public virtual void TakeDamage(int damage, bool critical)
    {
        if (isDead)
        {
            return;
        }

        Debug.Log(name + " take " + damage + " damage");
        ChangeHealth(-damage);

        healthBar.SetSliderValue(currentHealth, maxHealth);
        healthBar.ShowDamageText(damage, critical);

        if (currentHealth <= 0)
        {
            Dead();
        }
    }