Just like it did with the original Half-Life last year celebrating the seminal first-person shooters 25th anniversary with a major update, a documentary, and a 100% off sale Valve is celebrating the arguably even more influential Half-Life 2s 20th anniversary with, you guessed it, an update, a documentary, and a 100% off sale.Valve made the announcement, and detailed all of the changes, on a new website for the game. That update notably includes the usual mix of bug fixes and graphical improvements, a developers commentary track a practice that all Half-Life and Portal games following the release of Half-Life 2 benefited from as well as Steam platform level enhancements in the form of Steam Workshop support and the new Steam game recording.Every map in Half-Life 2 has been looked over by Valve level designers to fix longstanding bugs, restore content and features lost to time, and improve the quality of a few things like lightmap resolution and fog, Valve details on the site.Scroll way down for a much more exhaustive list of all of the changes. A larger enhancement to the game is the inclusion of Half-Life 2s episodic expansions, Episode 1 and Episode 2. Notably, and sadly, this does not include any confirmation of a conclusion in the form of the never-released Episode 3, though Valve does speak to its failure to deliver that ending in the two-hour documentary.We could have shipped it. It wouldnt have been that hard, Valves Gabe Newell says, sporting a new lewk while sending an entire generation of gamers into a dark spiral. My personal failure was being stumped. I couldnt figure out why Episode 3 was pushing anything forward.And, if you somehow havent somehow ended up with Half-Life 2 in your Steam library over the last 20 years, first congrats? That seems actually hard to do. Second, youll be glad to know its currently being offered, upgrades and all, for the low low price of $0.00 until November 18, just two days away. Add it to your library permanently by going here and clicking the green Download button, and will it to your grandkids.Speaking of downloads, Valves anniversary site also includes links to historical videos of the game, such as high-quality captures of previously unavailable E3 demos, as well as a host of new wallpapers and links to download or listen to the various soundtracks.