????????
      +---------
WXCFW | CQFMGGFN
       -WXCFW
        =====
        WWQGMG
       -WEEQXF
        ======
         ECCXUF
        -EXUGUW
         ======
           CNYPN
          -WXCFW
           =====
           ?????

base: 12
letters: CEFGMNPQUWXY
difficulty: intermediate