The next version of the game, Day of Defeat: Source, an update of DoD using the Source engine used for Half-Life 2, was released on September 26, 2005. Unlike previous releases of DoD, the game was only available as part of Half-Life 2 bundles available on Steam. Steam is now required to play DoD, because Valve was having problems with piracy. It makes significant changes to Day of Defeat's gameplay dynamics. Day of Defeat: Source was temporarily available for free download and evaluation from February 11-12, 2006.