LMQG
      +---------
MPVYV | TNVXNQXU
       -MPVYV
        =====
        ZGHTXQ
       -ZZXPLY
        ======
         LLYRWX
        - WRJUJ
         ======
          QMGGMU
         -QGLRMV
          ======
           QZMXR

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard