????????
      +---------
FNPHT | RRYNYTTR
       -FNPHT
        =====
        XNETWT
       - HUWPY
        ======
         TNYUGT
        -NEHGWX
         ======
          TPXXNR
         -TGRTFG
          ======
          ??????

base: 13
letters: EFGHMNPRTUWXY
difficulty: medium
missing: M