void SelectUnits()
    {
        ClearSelectedUnits();

        RaycastHit[] hit = Physics.BoxCastAll(rectCenter, halfExtents, Vector3.up);

        for (int i = 0; i < hit.Length; i++)
        {
            if (hit[i].collider.CompareTag("PlayerUnit"))
            {
                UnitMove u = hit[i].collider.GetComponent <UnitMove>();
                u.SelectUnit();
                u.CalculateOffSet(rectCenter);
                selectedUnits.Add(u.gameObject);
            }
        }
    }
    void SelectUnit()
    {
        ClearSelectedUnits();

        RaycastHit hitInfo = new RaycastHit();
        bool       hit     = Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hitInfo);

        if (hit)
        {
            if (hitInfo.collider.gameObject.name == "SkilledBuild")
            {
                UnitMove u = hitInfo.collider.GetComponent <UnitMove>();
                u.SelectUnit();
                u.CalculateOffSet(rectCenter);
                hitInfo.collider.gameObject.GetComponent <SkilledBuild>().panel.SetActive(true);
                selectedUnits.Add(u.gameObject);
            }
        }
    }