????????
      +---------
TTXYH | HHWLRXWP
       -YPNMH
        =====
         FXUXX
        -FHUMQ
         =====
          NGURW
         -PXRGH
          =====
           MNRTP
          -MRUNQ
           =====
           ?????

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