Zynga dominated social video games for PCs with "FarmVille" and "Zynga Poker." New versions for smartphones and tablets, being introduced this week in some markets, may determine whether it stays relevant.

Five years after becoming a hit on Facebook, the first mobile version of "FarmVille" will reach consumers in unnamed countries this week, ahead of a global rollout in coming months. "Zynga Poker" and "Words With Friends" applications for Apple and Android devices also will get facelifts as the San Francisco-based company seeks to shore up its foundation before introducing new titles later this year.

Chief Executive Officer Don Mattrick, who left Microsoft to take the helm at Zynga in July, is retooling the company to focus on games for phones and tablets, a market it ceded to others as the previous management remained wedded to Facebook and pursued real-money gambling. Many mobile games are free to download, with developers making money on in-app purchases and advertisements.

"We know what we need to do as a business is create hits and sustain them," Mattrick said in a telephone interview. "The team now understands that's the to-do list."

"FarmVille 2: Country Escape" will attempt to recapture many of the 400 million people who have played versions of the farming-simulation game since it became available for computers in 2009. The mobile version will offer free in-game currency to former players and the ability to shift virtual commodities such as water and sugar between the Facebook and mobile versions.

"We still have a huge, loyal following, and we're now bringing FarmVille to mobile in a really reimagined, mobile- first way," said Jonathan Knight, a Zynga vice president in charge of the title.

While the Facebook title helped launch Zynga to stardom and persuaded investors in its 2011 initial public offering that it would be a standout among Web-focused game developers, the mobile version will make its debut under different circumstances. Game makers are grappling with the fact that while they can grab millions of users with free titles, only a small percentage of those customers pay for extra items and many are fickle with their loyalties.

Zynga shares, which closed as high as $14.69 in March 2012, fell as low as $2.10 by November of that year, when the company was run by founder Mark Pincus, who remains chairman and chief product officer. Through yesterday, the shares had risen 48 percent since Mattrick arrived in July 2013. They fell 0.8 percent to $5.02 at 12:26 p.m. in New York.

Other companies have rushed into mobile with games that have proven addictive to millions of users. King Digital Entertainment the maker of "Candy Crush Saga" and one of the reigning social-game champions, said last month that it plans to raise at least $500 million in an initial public offering, funding that will help it create more titles.

The mobile "FarmVille" also faces competition from closely held Supercell Oy, founded in 2010 in Helsinki, whose "Hay Day" iPad game contains many of the same elements as "FarmVille."

"FarmVille on the tablet has the potential to reinvigorate the brand as older players come back, and it may attract some newer players, but I don't think it will be a monumental shift," said Michael Pachter, an analyst at Wedbush Securities in Los Angeles.

Mattrick said Zynga's mobile titles will beat the competition by passing "the Starbucks test," letting people make quick decisions while standing in line for coffee, yet having enough depth to occupy hours on a couch at home. The company's development teams are gaining better insight into their products from increased testing with consumers and more focus groups, he said.

As a result, the company also is adding better graphics and social interaction to "Word With Friends" and "Zynga Poker," both still leaders in their categories, according to AppData research. The upgrades give users more statistical information on players matched against them, helping people compete better and potentially keeping them more engaged, company executives said.

Mattrick said last year that the company would no longer try to convert some 350 million "Zynga Poker" players to Internet gambling after prospects dimmed for securing U.S. licenses.

Mattrick's goal is for Zynga to become the leading maker of free-to-play games in North America and Europe. The company is counting on acquisitions and a streamlined staff of about 2,000 to bridge gaps not filled by the core titles.

In January, Zynga agreed to buy U.K.-based NaturalMotion for $391 million in cash and 39.8 million shares. The acquisition adds two popular mobile titles, "CSR Racing" and "Clumsy Ninja," as well as access to technology that better replicates digitally the movements of people and animals.

Zynga cut at least 520 jobs last year, closed offices and said it would look for other areas to streamline the organization as Mattrick focuses development teams on his growth objectives.

"We're at scale and have gone through some of our growing pains and now we're getting things on track," Mattrick said. "We're committing ourselves to connecting the world through games."