????????
      +---------
NCEFF | EJEPRJCQ
       -QEEJP
        =====
        HJEXJJ
       -HJCXQW
        ======
          CEENC
         -NCEFF
          =====
          RCEPQQ
         -RRCECW
          ======
          ??????

base: 12
letters: CEFHJNPQRUWX
missing: U
difficulty: hard