XMZT
      +---------
ZTHGV | LRXHNTUH
       -LMUPG
        =====
         HWHLT
        -HLTGY
         =====
          MVPGU
         -MXPWJ
          =====
           XQWNH
          -ZTHGV
           =====
           TJZLT

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard