????????
      +---------
NWQGX | UQMTYMTT
       -JHRGR
        =====
         PPTGM
        -NWQGX
         =====
         QJGFQT
        -QYWHMF
         ======
          NFNRTT
         -QMXQHR
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: challenging
missing: L