When I first wrote the HL2 Tweak Guide, it proved immensely popular, and over time it has been updated several times. Unfortunately in recent times I haven't kept it as up to date as I should have, primarily due to the demands of writing many other new guides. However I have now taken the opportunity to completely revamp the guide, rewriting major portions of it to bring it fully up to date with the latest build of the Source Engine, which is being used in a range of games released by Valve, the latest being HL2: Episode 2, Team Fortress 2 and Portal. So while the guide is ostensibly for Half Life 2, it applies to all Source Engine-based games, hence the retitling of the guide. Given the technical improvements in the Source Engine over the past three years, it is definitely a fine platform for the new games Valve is releasing. As usual, this guide contains all the basic to advanced details you need to be able to tweak and customize HL2: Episode 2, or your Source Engine game, to look and perform the way you want it.