????????
      +---------
HECEQ | EGHRHXYX
       -RQRYM
        =====
         EEGQX
        -RQRYM
         =====
         XGRFHY
        - UGQXH
         ======
          HYRGXX
         -HXYXFG
          ======
          ??????

base: 12
letters: CEFGHMNQRUXY
difficulty: hard
missing: N