Half-Life: Episode 3 remains one of the great what-ifs in gaming history. Originally set to follow on from Episode 1 and 2, its cancellation instead left the series dangling on a cliffhanger it never directly resolved. Now, on the occasion of Half-Life 2's 20th anniversary, Valve has opened up about its development in a brand-new documentary that shows never-before-seen work-in-progress footage, a brand-new Ice Gun, and a raft of new concept art. You can see the gameplay segment from the documentary in the video below.PlayIGN's Twenty Questions - Guess the game!IGN's Twenty Questions - Guess the game!To start:...try asking a question that can be answered with a "Yes" or "No".000/250Among the details shown in the video, Episode 3 would have been set in the Arctic, and it would have focused on Alyx as a companion character. Aside from the Ice Gun, the footage shows a blob-like enemy that could split into multiple parts. According to the documentary, the team had complete a "collection of playable levels in no particular order" and expected to be able to release the game within a year or two.In addition to the new gameplay footage, writer Marc Laidlaw, founder Gabe Newell, and others also talk frankly about why it was never released, ultimately chalking it up to a lack of compelling new ideas and other reasons. At one point Laidlaw jokes, "Are we allowed to cry in this documentary?"We could have shipped it. It wouldn't have been that hardThe reason for Episode 3's cancellation has been the subject of much discussion over the years, not the least because Episode 2 ended on a grim cliffhanger. In an interview with IGN shortly before Alyx's release, Valve level designer Dario Casali described it partly as an issue of scope screep. Laidlaw would later reveal the plot in a story called "Epistle 3," featuring "Gertie Freemont" and "Alex Vaunt" plays on Gordon Freeman and Alyx Vance.Half-Life 2: Episode 3 would have been set in the Arctic and featured an Ice Gun. Image source: Half-Life 2 Documentary.It's possible to detect a lot of regret over the decision not to go through Episode 3. At one point Laidlaw jokes, "Are we allowed to cry in this documentary?" Others talk about how Episode 3 probably could have been released in hindsight. Newell says, "We could have shipped it. It wouldn't have been that hard. My personal failure was being stumped. I couldn't figure out why Episode 3 was pushing anything forward."Valve finally released Half-Life Alyx in 2020, sending the story spinning off in a new direction, but many fans remain wistful about Half-Life: Episode 3 (not to mention the long lost Half-Life 3). Now, 20 years after its release, Valve is celebrating Half-Life 2 amid unconfirmed rumors that a new game is in the works. In the meantime, it's worth watching the entire documentary, which delves deep into Half-Life 2's fraught development.Image source: Half-Life 2 Documentary / ValveKat Bailey is IGN's News Director as well as co-host of Nintendo Voice Chat. Have a tip? Send her a DM at @the_katbot.