????????
      +---------
TRQLR | LHGGQJPN
       -XPYFF
        =====
        TRTGQJ
       -TURWPQ
        ======
          HMUUP
         -HFXTQ
          =====
           PMWHN
          -RMLYR
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard