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Warning:Your Engine Version in the Source SDK must match the Engine branch of your mod! Failing to do this will result in Source SDK tools being unable to load required resources. See Source SDK 2013 for more information. This time around, the source code is not made available via an SDK launcher, but is instead hosted on Github. With this change, they updated the source code to the latest version of the Source-1-Engine for the HL2-based engine branch. In 2013, Valve phased out the Source SDK with the release of SteamPipe. It also lacks many of the HL2-compatible code's peripheral tools (including custom shader support) and cannot access HL2's content. Alien Swarm is totally free to play and its SDK includes source code, but it's source code for a top-down shooter. However, you cannot make a mod for Source 2009 you can make a content-only mod of a 2009 game by following Creating a Mod manually. This is the current version of the engine with Mac support. This is the most recent HL2-Based engine branch available. Only included for backwards compatibility reasons. Outdated - Original Half Life 2: Episode One mod. Half-Life 2, together with Episode One originally ran on Source Engine (Old Engine). Both of these engines are very different from each other, so it's good to know what the advantages are of a certain Engine. Change the SDK's engine version to the one you want. As you might have seen or heard it, there are two different iterations of the Source engine to choose when you're speedrunning Half-Life 2. Before starting a mod you need to choose which version of Source you will use.
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