(CNN) -- Early each morning, millions of farmers around the world rise to toil in their fields. By night, gangs of mobsters scheme and legions of poker players shuffle up and deal.





Sure, none of it's real. But the overwhelming popularity of so-called social gaming -- simple games that let people play with their friends on networking sites such as Facebook -- is changing the face of video games, experts say.





And as the maker of popular titles like FarmVille and Mafia Wars, San Francisco, California-based Zynga has ridden the games' skyrocketing popularity to the top of that emerging market.





For Zynga founder Mark Pincus, the formula for gaming success on Facebook, MySpace and other sites was as simple as it might seem counterintuitive: create simple games that people like but can easily set aside.





"We built the games so they could be played in a tab on your browser while you're on a conference call," said Pincus, a veteran Web entrepreneur who created Zynga in 2007.





Of course, they've been helped by the massive growth of Facebook, where the games are so popular they've spawned "fan" pages devoted to complaining about having to watch friends play them.





Facebook, with its 400 million users, is where the vast majority of people play FarmVille and Mafia Wars along with other Zynga titles like FishVille, Vampires, Café World, YoVille and Zynga Poker.





In all, more than 65 million people play Zynga games every day, according to media tracking company Developer Analytics.





Zynga's top title, FarmVille, is played by an estimated 75 million people each month --  roughly equal to the number who have played the classic arcade and desktop game Tetris during its entire existence.





The massive growth was satisfying but not altogether surprising to Pincus, whose previous startups had included Freeloader, a Web-based information-gathering service; tech-support company SupportSoft; and Tribe.net, an early social networking site from 2003.





He said that starting the game company, which he named after his late English bulldog, was an effort to fill what he considered a surprising void in most people's daily Internet use.





"I thought in 2007 that something had gone oddly wrong with the whole Internet experience," Pincus said. "I would have thought games would have been one of the top two or three experiences people had on the Internet."





What Pincus got right, according to gaming expert Scott Steinberg, was a sort of return to the "golden era" of games like Pac-man and Super Mario Bros.





"Video games actually appealed to a huge cross-section. They appealed to everybody," said Steinberg, publisher of DigitalTrends.com. "What happened is, as we went through the mid-'80s to the mid-2000s, you started to see gaming become more incestuous in terms of 18- to 34-year-old males making games for people just like them."





By contrast, three of Zynga's top five games -- FarmVille, Café World and FishVille -- have mostly female players, with many players outside the traditional 18- to 34-year-old range.





Those games all operate on the same basic premise. Starting with a simple farm, fish tank or restaurant, the player works to make it bigger and fancier, sharing items with friends and helping each other along the way.





Some of Zynga's early titles simply mirrored existing board and card games. It was Mafia Wars -- in which players team up to whack other gangs -- that first exhibited what would become the hallmarks of social gaming: simple, single-player action that's enhanced by teamwork.





With FarmVille, that formula would become complete.





Players plant virtual crops that can be harvested hours, or days, later. Along the way, they invite online friends to become their neighbors and help each other by sending gifts or helping with the farming. There's no way to "win," but players take satisfaction in building big, fancy farms that they can showcase to their friends.





"A farm is something that is internationally understood and known. It's cross
What did the founder say the key to success was? What games are played by millions? Who does social media gaming appeal to? When can you play Zynga games?
create simple games that people like but can easily set aside. social gaming huge cross-section. every day,
question: What did the founder say the key to success was?, answer: create simple games that people like but can easily set aside. | question: What games are played by millions?, answer: social gaming | question: Who does social media gaming appeal to?, answer: huge cross-section. | question: When can you play Zynga games?, answer: every day,