????????
      +---------
GTGFP | TPXWNMPN
       -GTGFP
        =====
        GNTTWM
       -UXUNFM
        ======
         UCCPEP
        -UGEWNW
         ======
          NCNXUN
         -NGGCWT
          ======
          ??????

base: 11
letters: CEFGMNPTUWX
difficulty: intermediate