Source Entities:Games

The Source engine has a large selection of games on it, and three of them were released at the same time. Some are "built off" each other in a branching and not-wholly-linear path. Functionality also is occasionally wildly different between games due to Valve's seemingly ever-shifting method of maintaining code.

Since it's not perfectly clear, on Source Entities, all text along the lines of "available since X game" means "available in X game, and every game that was released afterward". Some people instead think this simply means that it's been in every Source game since the release of one game, implying the feature was backported (usually not the case). "Since Alien Swarm" means a feature is available in Alien Swarm, Portal 2, and Counter-Strike: Global Offensive.

Supported games

 * Alien Swarm
 * Counter-Strike: Global Offensive1
 * Counter-Strike: Source
 * Day of Defeat: Source
 * Half-Life 2
 * Half-Life 2: Deathmatch
 * Half-Life 2 Episodes
 * Left 4 Dead
 * Left 4 Dead 2
 * Portal
 * Portal 2
 * Team Fortress 21

Possible games
These games might be considered for documentation on this wiki once the main 12 are finished. This list is not necessarily complete but they are the games most likely to be incorporated. For the time being, the specifics for supporting these games have not even been worked out.
 * Alien Swarm: Reactive Drop1
 * Age of Chivalry
 * Black Mesa1
 * BrainBread 2
 * Contagion
 * Dark Messiah of Might & Magic
 * Day of Infamy
 * Dear Esther
 * Dino D-Day
 * E.Y.E: Divine Cybermancy
 * Fistful of Frags
 * Garry's Mod1
 * INFRA
 * Insurgency
 * No More Room in Hell
 * Nuclear Dawn
 * Pirates, Vikings, & Knights II1
 * Sin Episodes
 * Synergy
 * The Ship
 * Vampire The Masquerade - Bloodlines
 * Zeno Clash

1 - These games seem to still be under significant active development. Keeping the documentation up to date is very important.

Timeline
Counter-Strike: Source was the very first Source game in 2004, followed by Half-Life 2 in a matter of weeks. Half-Life 2: Deathmatch came less than a month later. Day of Defeat: Source released in 2005. Half-Life 2: Episode One released in 2006, building off Half-Life 2's codebase (this was when the 2006 SDK was released). Half-Life 2: Episode Two came in 2007, and all code that was new with the game was integrated directly into Episode One's code (this branch is referred to as "Episodic", and this was when the 2007 SDK got released). Portal and Team Fortress 2 were also released on the same day as Episode Two, forming the Orange Box. This makes up the "classic" Source games.

All of Source's "modern" games follow a pattern of being built directly off the previous game and inherit all that game's features (and sometimes bugs). Left 4 Dead came out in 2008, and drew code from a mix of the 2007 SDK and Counter-Strike: Source. Left 4 Dead 2 came in 2009 and was built directly off Left 4 Dead. Alien Swarm was released in 2010. Portal 2 was released in 2011, but was actually built off a very early build of Dota 2, which itself was built off Alien Swarm. Counter-Strike: Global Offensive came out in 2012, and is technically the last Source game.

In 2013, Valve published the 2013 Singleplayer SDK, which is not very different from the 2007 one though all the "classic" singleplayer games now run on this branch of Source. Dota 2 came out in 2013 (though it is not related to the 2013 SDK at all). In 2014, Valve created the 2013 Multiplayer SDK, which was a current fork of code in Team Fortress 2 (though missing most tf2-specific code, instead coming with hl2 code like Singleplayer did). The 2013 Multiplayer SDK is now used by all the "classic" multiplayer games. In 2015, Dota 2 was ported to Source 2 and was the first game to run on the engine. The Source 1 version of Dota 2 is no longer available.

Orange Box
The Orange Box is the name given to a package of games released by Valve all on the same day. It's made up of Team Fortress 2, Portal, and Half-Life 2: Episode 2 (along with HL2 and Episode 1 bundled) which were all close to being finished at the same time anyway. On Source Ents, due to the fact that the HL2 Episodes run on the exact same code (in source and binary), "The Orange Box" only refers to TF2 and Portal 1 (excluding Ep 2), and things that were added in all three games at once will be noted as being added in the HL2 Episodes because they came first and technically, all code new with Episode 2 was really just an update to the Episodic branch. While this is odd, it clears up any ambiguity.

The Half-Life 2 series
"The Half-Life 2 series" refers to all these games: Portal is included because it comes with nearly all code in the Episodic branch. Evidence exists in that many Half-Life 2 NPCs and weapons may be spawned, and if equipped, the HEV suit shows the Episode 2 flashlight HUD element. Portal 2 is not explicitly included, but many things in Portal 1 ended up being available in Portal 2 as well.
 * Half-Life 2
 * Half-Life 2: Deathmatch
 * Half-Life 2 Episodes
 * Half-Life 2: Lost Coast
 * Portal

Engines
Originally, Source Entities was to also document GoldSrc and Source 2 material, though it's being considered if splitting up by engine into sister wikis would work better. Support for Quake is not being considered.

"Historic" notes
Commonly, VDC notes things that were added to Source at the time of a certain game, yet these features were also backported to older Source games. SE will not do this because it creates ambiguity. Being clear and accurate is more important than an otherwise trivial fact about a feature.