"Project Z" has the sinister ring of a Cold War secret weapons project but it's good news for the millions of players of Zynga's social media games as the internet giant gave the mysterious moniker to an upcoming new service and unveiled more games set to get Facebookers clicking.

The most famous of Zynga's fiendishly addictive pastimes come under the 'Ville' label with Farmville, in which players cultivate their own virtual plots and try to get the best harvest safely home. Last month, Farmville was still the third most popular game on Facebook two years after its launch.

The latest 'Ville' game was released in Chicago yesterday and takes players back to medieval times, challenging them to build their own magical kingdoms. It's called, of course, CastleVille. Trading, battling monsters, magical fantasy and working with friends are all there and Zynga claims to have upped their game when it comes to the look and feel of the game, which, like a movie, has its own original soundtrack recorded by a full orchestra and choir.

CastleVille Facebook Page Screenshot and link to it © Zynga/Facebook

Hidden Chronicles was also trailed at the launch. Zynga says the game is a new departure into the hidden object genre, demanding good recall and puzzle-solving skills from its players. Describing the look of the game as 'soft photorealism', Zynga promises a sophisticated and engaging way to while away the hours.

Gamblers will head to the new Zynga Casino, a platform that will now host the more than 35 million Zynga Poker players as well as those drawn in by the brand new Zynga Bingo.

Smart phone players will get the chance to play zookeeper as they build a Dream Zoo collection with the new app game and those who've built their Facebook criminal kingdom to its limit in Mafia Wars will want to start up a new battle with the forces of law and order in Zynga's first sequel, Mafia Wars 2, which also debuts on the new social network Google+.

While the new Project Z remains somewhat mysterious, Zynga says it will use Facebook's ability to connect with other programmes and websites to open up a 'social playground'. The world's largest social game developer must be pretty confident of success as they're inviting would-be users to sign up and grab hold of unique player names called zTags.