public override void Update(EnemyAgent agent)
    {
        //update position of the player
        agent.SetPlayerTarget();

        if (Vector3.Distance(agent.GetNavMeshAgent().destination, agent.transform.position) < agent.GetAttackRange() + 0.5f)
        {
            agent.SetState(AttackState.GetInstance());
        }
        if (Vector3.Distance(agent.GetNavMeshAgent().destination, agent.transform.position) > agent.GetFollowRange() + 0.5f)
        {
            if (agent.GetIsWaveEnemy() == false)
            {
                agent.SetState(PatrolState.GetInstance());
            }
            else
            {
                agent.SetState(ChargeBaseState.GetInstance());
            }
        }
    }