
Codename: Gordon, often referred to as Half-Life 2D, is a two-dimensional Flash-based side-scrolling shooter developed by Paul "X-Tender" Kamma and Sönke "Warbeast" Seidel. Created under the banner of Nuclear Vision, the game was made available free of charge via Valve Software's Steam digital distribution platform as a promotional effort for the upcoming release of Half-Life 2. It was later taken down from Steam's catalog due to circumstances tied to the developer's financial insolvency. The project initially began as a fan-made endeavor by Kamma and Seidel, inspired by promotional material for Half-Life 2. The duo soon transitioned into official development for Nuclear Vision, who then introduced the game to Valve, the creators of the original Half-Life series, resulting in its distribution through Steam.
Codename: Gordon offers a reimagined take on the narrative of Half-Life 2, featuring settings drawn from both Half-Life and Half-Life 2. Throughout the journey, Gordon Freeman, the central figure from the official games, encounters key figures from the Half-Life saga and seeks to uncover the cause behind the vanishing third dimension. The game begins with Gordon Freeman in a harbor zone. After navigating through a group of zombies and headcrabs, Gordon comes across Barney Calhoun, a major figure in the later Half-Life games. Barney informs Gordon that an "entire dimension" has vanished and mentions that the scientific team is investigating the issue. Due to his injuries, Barney is unable to move and hands Gordon his pistol, urging him to leave without him. In the second chapter, the player encounters Eli Vance and his daughter Alyx, who instruct Gordon to take their vehicle, which will aid in reaching City 17, apparently the epicenter of the issue. They also advise Gordon to speak with Dr. Kleiner about his new device, the gravity gun. Shortly after, the player locates Dr. Kleiner, who expresses his concerns about the missing dimension and hands Gordon the gravity gun as mentioned by Eli and Alyx. After fending off an alien attack and passing through a heavily fortified prison guarded by Combine forces, Gordon arrives in City 17, where he meets the G-Man. He tells the player he has been anticipating his arrival and denies responsibility for the missing dimension, instead claiming to be "just a minor player in a dark game orchestrated by greater forces." Shortly afterward, Gordon faces a strider — a massive three-legged combat unit — which is revealed to be the cause of the issue. Upon defeating it, a portal opens; stepping through it, Gordon is transported back to the third dimension.