????????
      +---------
LQWXQ | LTTMPHJW
       -LQWXQ
        =====
         YPGGH
        -WNPXT
         =====
          PMJGJ
         -PULFJ
          =====
           PQMRW
          -LQWXQ
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard