????????
      +---------
URPYX | PRTQHQWN
       -URPYX
        =====
         WNGWQ
        -YXMUG
         =====
         UJJYQW
        -RWTJMX
         ======
          RLPVHN
         -JWRWVG
          ======
          ??????

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