NWZH
      +---------
YMMVW | UVTWPMRU
       -YMMVW
        =====
        GYLWRM
       -GNWMHN
        ======
         GJRGLR
        -NXXVHZ
         ======
          YJGRTU
         -GHHVLH
          ======
           YURMW

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
missing: Q