????????
      +---------
WGEEQ | FWWLFNPG
       -GQEMR
        =====
        WUWWPN
       -QFLERG
        ======
         WLRLMP
        -WUYEWY
         ======
           GQGFG
          -WGEEQ
           =====
           ?????

base: 13
letters: EFGLMNPQRUWXY
difficulty: medium
missing: X