????????
      +---------
JFQLG | XGWLJHYW
       -RQUPW
        =====
        FTUJPH
       -FJLJUT
        ======
         YXWRJY
        -YXPJYP
         ======
           NHMXW
          -HPFGJ
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard