LPF
      +--------
RRPXP | PFPJHUN
       -GYNWX
        =====
        RRYXYU
       -RQLTUR
        ======
          UGGFN
         -UWYJN
          =====
           HJTQ

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