????????
      +---------
GWYRU | WLGXJXMZ
       -RGVZJ
        =====
         NWGPX
        -ZXPQY
         =====
          ZLQVM
         -RGVZJ
          =====
          LXLQXZ
         -LNHHWT
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard