HFF
      +--------
HGFRL | QMXMXTH
       -XYQUH
        =====
        LTURJT
       -LFHPXF
        ======
         LTNULH
        -LFHPXF
         ======
          LGWFG

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
hints: Y << M, N << R
missing: W