Included in the Source SDK are:

• The Hammer World Editor, which provides the capability of creating custom levels for Source engine-based games
• Valve's custom Faceposer tool that allows users to produce choreographed sequences in the Source engine
• A model viewer that allows artists to preview models and their animations quickly and easily
• Source code that allows mod makers to create their own game based on Half-Life 2 or Half-Life 2:Deathmatch
• All of the tools required to make build custom textures and models for Source engine games

Future Source SDK updates will provide new development tools, as well as source code for creating single and multi-player mods that utilize the latest Source engine features.

The update is available now via Steam.