Zynga is preparing the next in its series of "Ville" franchise offerings and this one offers a medieval setting called CastleVille. 

Two of its predecessor games, CityVille and FarmVille, are among the most popular games on Facebook at a time when the San Francisco-based gaming giant prepares for its upcoming IPO.

In the soon-to-be-released CastleVille, players build and share kingdoms with virtual friends in a mysterious world, surrounded by a shadowy, unsettled territory known as The Gloom.

The Gloom is filled with plants and animals and dangers, as well as the human characters that players will meet while clearing land to build their castles and kingdoms. There are five announced characters so far, but the company has others it will introduce as the game develops.

Once you meet and engage with these characters, the storyline behind this virtual world is gradually revealed to you.  Whereas The Gloom is infused with whatever force brought sadness to the world, the kingdoms you and other players build are brightly lit spaces with buildings you construct by cutting down trees and unearthing rocks, etc. There are ponds, rivers, plants and animals, including a little Twitter-like blue bird that arrives to bring messages that help to introduce characters to one another.

The overall user experience is what Bill Jackson, Creative Director at Zynga Dallas, which developed CastleVille, calls "streamlined social gaming that allows for much faster interactions with your friends. What we offer is a believable fantasy world in a social space. We think we have a large, rich narrative that will continue to evolve over time."

It features numerous sound effects and animations, animals like chickens that grow over time, and evil, attacking creatures, as well as a currency you can exchange with other characters.

The game unfolds in different ways for each player, depending on what choices you make and how engaged you become with other players and the characters built into the game, like The Duke, The Fair Maiden, and The Cupcake Slayer.

“The incentives are all to make it more social,” says Jackson. “The game rewards social playing. Just like in real life, everything is better with friends. It’s more fun.”

This narrative engagement required Jackson’s team to work much like  screenwriters do when creating a feature film. They have developed detailed backstories for each character that will be revealed slowly based on usage.

“We’ve gone through many iterations to create the characters,” he says. “We have great documents on each one.”

Zynga has also created an original soundtrack for the game, using a 75-piece orchestra and full choir in Seattle.