????????
      +---------
YWFYX | FHJUTHUQ
       -YWFYX
        =====
        QMUQUH
       -RTGJXR
        ======
         XWHLWU
        -TXWQPH
         ======
          YRNGGQ
         -PXXJYT
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium