????????
      +---------
PWUUF | GQQJGWXX
       -MXJHY
        =====
         UNXFW
        -THHTX
         =====
          WMMFX
         -YMMWG
          =====
          PNNQQX
         - FPUYR
          ======
          ??????

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