French game publisher Mediastay announced Monday that it has secured a €15 million ($21.5 million) investment from Iris Capital and Idinvest Partners (formerly AGF Private Equity). The company, which has headquarters in France, Brussels, and San Francisco, was the first French advertising company to be accredited by Facebook to provide advertising solutions to app developers.

Founded in 2000, the company publishes online sweepstakes games such as Kingolotto.com, Kingojackpot, Kingomusic, and Luckysurf.com, as well as casual games like DiamondsQuest, JungleSnake, and Yacado.com. Last summer, Mediastay launched a new payment solution, OfferMatch, with the aim of monetizing the games by allowing users to make micropayments for goods and services. More than 25 million brands across 14 countries are working with Mediastay’s platform, and in 2010, the company generated more than $25 million in revenue.

“Idinvest Partners is very pleased to support Mediastay's strong growth, as performance marketing is becoming a major factor in the advertising business,” said Idinvest partner Matthieu Baret in a statement. “This investment will indeed allow the company to accelerate the development of its monetization solutions in Europe while strengthening its presence in online and social games. We've been following the company for several years now, and we are delighted to participate in this exciting undertaking.”

Mediastay plans to use the new funds to build up its audience through the launch of new websites and the release of new Facebook and mobile applications. Additionally, the company plans to “strengthen” its current team of 60 employees.

"We are pleased to welcome highly-regarded investment firms Iris Capital and Idinvest Partners as new partners, alongside HighCo and Turenne Capital. Mediastay now has the capacity to substantially accelerate its expansion and benefit fully from its unique positioning in a market halfway between the very dynamic online gaming industry and the performance marketing sector," said Mediastay CEO Jerome Balmes in a statement.