TMEG
      +---------
GWGQG | MXTUJFEQ
       -GWGQG
        =====
        UMWTQF
       -UGQRXP
        ======
         GFRJJE
        -GQJPTJ
         ======
          YUMXUQ
         -YYJRQE
          ======
           YYXRU

base: 13
letters: EFGJMPQRTUWXY
difficulty: medium