????????
      +---------
PRFER | NPFWLPYH
       -PRFER
        =====
        YUGPNP
       -YMYPMG
        ======
         FWULPY
        -FLHFYR
         ======
          YNEYLH
         -YRLYGM
          ======
           ?????

base: 12
letters: EFGHLMNPRUWY
difficulty: medium