LHR
      +--------
XTQLX | ULXRYYL
       -WFRJQ
        =====
        JUYXNY
       -JUFGWF
        ======
          QPHPL
         -QGPTN
          =====
           XMWU

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