????????
      +---------
PXUZH | HHLRMVLN
       -PXUZH
        =====
         TUJLV
        -JJLGT
         =====
         NPNJHL
        -NWURVH
         ======
           JQTNN
          -PXUZH
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
missing: Y