????????
      +---------
NNTRW | QLMXHWGN
       -JQGFQ
        =====
        RUQQXW
       -RJWJYY
        ======
         RWRXWG
        -RGYHFQ
         ======
          RYWPJN
         -RYJGLW
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard