????????
      +---------
REFME | FFQJLRXF
       -REFME
        =====
         NNEER
        -HLJGL
         =====
          XMWJX
         -QJWRJ
          =====
          RRGNHF
         -RGGNXT
          ======
          ??????

base: 13
letters: EFGHJLMNQRTWX
difficulty: medium