GameStop Corp. launched a free gaming app for Android smart phones Tuesday. The new portal includes more than 300 games from the Kongregate game service that Grapevine-based GameStop bought last year. Getting ahead of the surging popularity of downloadable games and games on smart phones is critical for GameStop.

The company makes the largest share of its profit on buying and reselling used game discs and cartridges for consoles, a market that will probably shrink as a growing number of titles are delivered online rather than on physical media. The new Kongregate Arcade app is essentially a portal through which Android users can access hundreds of free games. It will make money through advertising.

The games use Flash software, which many phones running Google Inc .’s Android software support. But Apple Inc .’s iPhone , iPod Touch and iPad devices do not support Flash. GameStop did not say if it plans to bring an alternate version of the Konregate app to Apple’s machines. The Kongregate app will be advertised in GameStop’s 4,600 U.S. stores.

While digital delivery of large-scale games to living room consoles could take years to get off the ground, sales of games for smart phones are already big and growing.  Video game software sales for consoles such as the Xbox 360 and handheld devices such as the Nintendo DS totaled $10.1 billion in 2010.

But that figure was down five percent from 2009. Research firm and app developer Asymco estimated this week that sales from app-based games could surpass traditional game sales in four years.