????????
      +---------
EGTXG | QQRWQEFR
       -EGTXG
        =====
        XWLQPE
       -XQUGFX
        ======
         FMPGFF
        -XQUGFX
         ======
          EUMMNR
         -ERMEUR
          ======
          ??????

base: 13
letters: EFGLMNPQRTUWX
difficulty: medium