????????
      +---------
QLWML | MJGYQTLQ
       -NWULP
        =====
         JJHNT
        -YLTGQ
         =====
         QQXLUL
        -QHWPPG
         ======
           XRGQQ
          -XPWQM
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
missing: F