????????
      +---------
PHTGP | ELLYLMYQ
       -TMXHR
        =====
        XEPQYM
       -XRQYQU
        ======
         PUUYRY
        -UFXEQL
         ======
          PXURTQ
         -UFXEQL
          ======
          ??????

base: 13
letters: EFGHLMPQRTUXY
difficulty: challenging