Unsuspecting art lovers at the Smithsonian Museum of American Art and National Portrait Gallery saw some strange things going on in the galleries not too long ago.

Groups calling themselves Staves and Knaves dashed around the museum sporting faux mustaches or black skinny ties, occasionally stopping to consult documents, decode a painting or send a text message that would return a clue.

But these groups were doing much more — their actions would determine the fate of the imperiled Terra Tectus, the imaginary world around which Pheon, the museum’s newest alternate reality game, is based. And their role in the game didn’t end at the game’s launch. On Oct. 8, the yearlong online version of Pheon will be launched on Facebook and Twitter so participants can play from anywhere.

Participants are split into two teams — Staves and Knaves — and how well they complete each mission, as judged by other players, will determine how many points they earn. The team with the most points gains control of Terra Tectus.

As game designer John Maccabee describes them, Staves are the protectors of the Earth, while Knaves are its connoisseurs. In the course of game play, the groups are charged with “proving humanity’s worth” within Terra Tectus.

At the launch event, participants were all over the museum, using the artworks on display as clues to complete their assigned quests. Mike Wilkins’ “Preamble” to the Constitution, spelled out with license plates, held a secret code that would be used later on. Players visited a portrait of John Quincy Adams’s wife, Louisa Catherine, playing the harp and sang the tune on her sheet music into their cell phones to receive another clue. They re-created Deborah Butterfield’s bronze horse sculpture “Monekana” in aluminum foil.

The hands-on game gave the museum’s collection new life for the day, but that won’t end once Pheon hits the Web. Georgina Goodlander, interpretive programs manager for the museum, said online players will have to use the museum’s collection database to complete many of Pheon’s missions.

While the online portion of the game may not require a visit to the museum to participate, Goodlander hopes it will create greater awareness of what the museum has to offer.

The game is the second designed for the museum by Maccabee. Maccabee said he wrote the history of Terra Tectus and worked out how it functions. Maccabee has woven historical fact into his story of Terra Tectus. He became fascinated with 19th-century Danish scientist Hans Christian Oersted, who discovered electromagnetism, and made him a key character. In Maccabee’s story, Oersted’s discoveries allowed him to cross over to Terra Tectus, where he lives.

Players will receive clues from Oersted and other characters via Twitter throughout the online portion of the game.

Game participants will be encouraged to go beyond their computers to fully participate. Maccabee and game expert Sean Mahan developed missions that Fwill prompt players to “document, perform, make or discover” something, Maccabee said. After completing the mission, they will have to post photos or videos to Facebook for other players to vote on.

While game organizers predict Pheon will be fun for participants, they also hope it will generate an interest in the Smithsonian American Art Museum from teenagers and young adults. “It’s about looking around in an unconventional way,” Goodlander said. “It shows that museums can be fun and social.”

Results from the launch event determined which team would start with control of Terra Tectus. More than 150 people split into 60 teams played, with Staves beating out the Knaves by just one team.

“There’s nothing more fun than a close race,” Maccabee said.