void OnTriggerEnter(Collider other)
    {
        UnitRange range = other.GetComponent <UnitRange>();

        if (range != null)
        {
            if (m_CoreType == 1)    //  maincore는 모든유닛들이 공격
            {
                UnitBase unit = range.transform.root.GetComponentInChildren <UnitBase>();
                unit.AddDestroyTarget(m_CoreID);
            }
            else                    // subcore는 지상유닛만 공격함
            {
                UnitWalking unit = range.transform.root.GetComponentInChildren <UnitWalking>();
                if (unit != null)
                {
                    unit.AddDestroyTarget(m_CoreID);
                }
            }
        }
    }