????????
      +---------
RJUUU | LQGGPHTR
       -RJUUU
        =====
        UPYYMH
       -UFHFFX
        ======
         QNXTHT
        -QUXPPU
         ======
          QXNPRR
         -MJYMMX
          ======
          ??????

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