Valve's Steam store framework has steadily become the focal point of digital PC retail since its inception in 2003. Valve, never a company to rest on its laurels, has always implemented new initiatives to push the service forward, such as effective use of sales on a daily and seasonal basis, or integrating Steam services into retail games.Its latest push was releasing the Steam Mobile app for iOS and Android devices in January, which allows PC and Mac players to purchase their games while they're on the go.According to Kutta Srinivasan, an engineer at Valve who worked on the app, the idea for Steam Mobile came directly from the customers. The service was initially released as a beta, where users could apply for an invite, but it was very short-lived."We had to build out some new Steam back-end services to allow the application to function properly on mobile devices," said Srinivasan. "The beta period, which ended up being quite short, was a period of time in which we were able to verify that the new servers could handle the load of tens or hundreds of thousands of connected mobile devices."Srinivasan said the technical reason for tailoring the Steam backend for mobile was that the existing Steam client operates by staying connected to Valve's online servers during the player's session. Valve needed to adjust to the fact that users' devices have varying levels of connectivity, whether through WiFi, 3G or no connection at all.One look at the new app, and it's clear that you're in the Steam service. Despite being on a smaller screen with a different layout, the design aesthetic is very reminiscent of its PC counterpart.Achieving a UI that is "uniquely Steam across multiple platforms" was a major goal for the team. The company wanted to do so without "sacrificing usability paradigms to which customers on a particular platform are accustomed.""We ended up using some navigation and presentation UI elements that are consistent with other popular mobile applications (e.g. the global navigation fly-out menu), which allowed us to do more with the application than the build-in basic navigation controls on each platform," said Srinivasan.Steam Mobile isn't a one-and-done thing for Valve either, as the company has plans to expand the service moving forward. Features it hopes to roll out in the near future include better screenshot support and the ability to view your game library.Looking to the future of the app, Valve want to make sure "All relevant Steam community and economy features are accessible from your mobile device," said Srinivasan. "We'd love to see individual games hook into the service and provide mobile optimized web pages and experiences that we can link to from the game description pages. In general, we have a healthy list and expect it to grow, with new opportunities presenting themselves as the list becomes more robust."With strong community features built into the existing Steam experience, Valve wanted to ensure that it carried over to the mobile experience. To this end it has been successful, with chat being the most used community feature at present, as several million messages are sent per day from mobile devices.Eventually, Valve wants to use Steam Mobile to help grow the overall Steam user-base. "Phase one was just about getting existing customers connected when they're away from their computers," said Srinivasan. "As we discover the ways they interact with what we've provided, we expect to learn more about how to make it more universal."After recent security issues with Steam on PC, Valve also wanted to ensure that the mobile version would not add to its troubles, with Srinivasan stating that security was paramount from the start."In an upcoming [update], the Steam app will be able to act as a two-factor authentication device to bolster the security on your primary Steam account," he said. "If your phone is lost or stolen, simply changing the password on your account will invalidate the tokens used by the application to access Steam."So far, at least, it sounds like users aren't driven away from using the service by security issues. While Valve has never commented or given specific sales numbers for Steam, Srinivasan simply added "we are very happy."