????????
      +---------
MFTUG | QGTHLGMH
       -MFTUG
        =====
        JHTPWG
       -JHRFQX
        ======
          LTHFM
         -PXLXF
          =====
          MYYHHH
         -MYGUTU
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
missing: N