Facebook just rolled out a standalone, Steam-like solution for casual games called Facebook Gameroom.
Facebook Gameroom is a Windows desktop application available for free download for users running Windows 7 or higher, and
is actually offers the same functionality with the Games bookmark on Facebook. It lists most of the games you can find on the social network. Games are downloaded and saved locally.
Gameroom uses the Unity engine to power its casual games as part of the partnership between Facebook and Unity Technologies.
With Gameroom, Facebook could eventually move closer to a future virtual reality social environment, as the company discussed in October during the Oculus Connect conference.