In September 2008, Valve announced that the company would begin to host modifications based on the Source engine on the Steam system, available for download through the system. The developers of the modifications are then given the ability to deliver updates for their projects through Steam; other modifications are available, but cannot make use of this distribution service. In addition, the modifications can be augmented with Steamworks features such as achievements, improved Steam community functions and individual player statistics. Each modification is free to download, but requires the client Steam account to possess at least one Source game developed by Valve, such as Half-Life 2, Counter-Strike: Source or Team Fortress 2. As of December 2012, 13 modifications are available through S