????????
      +---------
LXZWX | WPYHNGHU
       -LXZWX
        =====
        XGYNHG
       -XXXZRZ
        ======
         RQUYTH
        -RHNZLT
         ======
          LMYVQU
         -PPVWGW
          ======
          ??????

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