????????
      +---------
YPZQU | GMZHTYYG
       -YPZQU
        =====
        JHXLJY
       -JTPMTX
        ======
         JGWTNY
        -JNNUZJ
         ======
          JNRMJG
         -JRUHRV
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard