JUPF
      +---------
WQNQU | NHHQTQUT
       -UQRRN
        =====
        HUNHHQ
       -HQRFJH
        ======
         WRFTRU
        -WJJXHQ
         ======
          HJWJWT
         -HWTXNF
          ======
            JFQR

base: 12
letters: FHJNPQRTUWXY
difficulty: challenging
missing: Y