????????
      +---------
PRRCL | QLPCUPQN
       -QQQPCP
        ======
         QRNNFQ
        -HNUQGL
         ======
          QCUFXN
         -QQQPCP
          ======
          ??????

base: 12
letters: CFGHLNPQRUWX
missing: W
difficulty: hard