PUWL
      +---------
TPVQQ | LVMTMPQH
       -TPVQQ
        =====
        PZLPJP
       -PUJGPY
        ======
         PHUXPQ
        -PRVJNN
         ======
           XNQLH
          -XHXUU
           =====
            WRVN

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium
missing: W