????????
      +---------
RRJHL | TWTJNNQF
       -WTRRG
        =====
        XQMHQN
       -XMQLGU
        ======
         FJQRRQ
        -FLWWQW
         ======
          UYHHXF
         -FQFGPP
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
attributes: good referencing