Zynga.com launched with CastleVille, Words With Friends, CityVille, Hidden Chronicles and Zynga Poker, along with a promise of lots more social games by the San Francisco-based firm and outside developers.

"Zynga.com is designed to make it easier for you to play with friends," Zynga founder Mark Pincus said in a blog post.

"We've invested heavily to build a network and infrastructure tuned for delivering social gaming at scale."

Zynga played up its online games community as an expansion of its partnership with Facebook rather than a quest for more independence.

Zynga rose to success on the popularity of it titles at Facebook, where millions of users enlist friends in either collaborative or competitive online play ranging from poker to growing virtual crops or building cartoon cities.

Zynga.com is connected to the Facebook "social graph" so game play and the actions of friends involved will follow users between the online venues, Zynga general manager Manuel Bronstein told AFP.

"I see this as a great manifestation of our relationship with Facebook that goes deeper into gaming," Bronstein said.

"In the morning you may check your news or social feeds on Facebook and then play games, but late in the afternoon you might just want to play, so you go to Zynga.com"

Along with keeping people connected with Facebook play companions, the Zynga website features ways to speed up progress in games and find "zFriends" who share one's passion for certain titles.

Zynga.com was also crafted as a platform on which third-party developers could make titles available to the 240 million people who play the company's games each month.

Zynga jumped into the stock market with a billion-dollar listing in December.

Offering 100 million shares -- one seventh of the company's total -- at $10 each, the maker of Facebook games FarmVille, Mafia Wars and Words With Friends was valued at a whopping $7 billion.

Zynga's stock price rose slightly to $14 a share on the NASDAQ in after-hours trading that followed the launch of the online games community.

Zynga games are free to play but the company makes money by selling virtual in-game goods to players and serving up advertising. The company sees the potential for revenue to grow if players flock to zynga.com.

The gripping science fiction adventure meshes powerful action and interactive storytelling that lets players shape which direction the saga takes, with decisions changing the outcomes of situations and the fates of in-game characters.

In a unique move, studio BioWare crafted the "Mass Effect" franchise in three parts with a compelling overall story arc and players' actions in one game following them into the next.

Allies made or friends lost in one game changes who is at the side of a player's character, and thusly their options, in sequels. Players can opt to not import characters' reputations from earlier games so they can start fresh.

Alliances promised to be paramount in "Mass Effect 3," which was billed as putting players "on the front lines of this all-out galactic war."

"The entire scale of the game is bigger than anything we've ever done," said "Mass Effect 3" executive producer Casey Hudson.

He touted the game as delivering "intense action, deep customization and raw emotional power."

The games pit the main character, a male or female version of Commander Shepard depending on player preference, against an ancient race of machines called "Reapers" intent on wiping out organic life in the cosmos.

The third version of the game opens with Reapers invading Earth, according to demo software released free online last month. Shepard was called on in the demo to enlist the help of races from other planets to fight the Reapers.

"You along with a team of battle-hardened soldiers are the only ones who can save Earth, and the galaxy, from complete annihilation," the game makers said in a release.

"Each decision and every action could have devastating and deadly consequences in your journey."

"Mass Effect" trilogy publisher Electronic Arts declined to disclose how many games had been pre-ordered, other than to say the number "well exceeded" those for the second installment.

Mass Effect software released on Valentine's Day quickly became the second-most downloaded videogame demo in EA history, behind only "Battlefield 3."

The franchise has received more than 250 awards and 100 perfect scores from videogame critics.

"Mass Effect 3" was priced at $60 and version were tailored for play on Xbox 360 and PlayStation 3 videogame consoles as well as personal computers powered by Windows software.

The Xbox version of the game was adapted to allow players to tap into voice and motion command capabilities of Kinect accessories.