HLF
      +--------
QTWLJ | RQPGMJP
       -XYRUU
        =====
        YLLQFJ
       - PRNJL
        ======
         QTQLTP
        -QLJPUQ
         ======
          QUWYX

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