????????
      +---------
PXULY | RTGLGLFR
       -PXULY
        =====
        QTFXML
       -QPXNUY
        ======
          LGWYF
         -FXMXN
          =====
           FHUPR
          -JXYRL
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: intermediate