????????
      +---------
PEXEQ | UWFQJJGE
       -PEXEQ
        =====
        WQGXQJ
       -WWXFGH
        ======
         HXPJXG
        -HGWXLW
         ======
          WLHEPE
         -HJRGXE
          ======
          ??????

base: 13
letters: EFGHJLPQRUWXY
difficulty: hard
missing: Y