????????
      +---------
GXGGH | LXLCHRHH
       -GXGGH
        =====
        NJJHJR
       - GXGGH
        ======
         PHMGNH
        -PWCJMX
         ======
          NRPHWH
         -NGLLWG
          ======
          ??????

base: 12
letters: CGHJLMNPRUWX
difficulty: medium
missing: U