Eli Fisker, a librarian in Denmark, is EteRNA's top player. EteRNA's puzzle-solving game players (like Fisker and 40,000 others) deciphered the structure of the Mason-Pfizer monkey virusD—which had stumped scientists for 15 years—in just 10 days. Using EteRNA, an online video game, players design RNA as part of a weekly competition. In this series on gaming, CNN investigates how everyday gamers are making huge contributions to science and medicine.