Entropy: Zero 2
Developer(s)	Breadmen
Publisher(s)	Breadmen
Director(s)	Johnny Richardson
Programmer(s)	Derek Dik Allen Jones
Artist(s)	David Driver-Gomm
Writer(s)	Johnny Richardson
Composer(s)	Spencer Baggett
Series	Half-Life
Engine	Source
Platform(s)	Windows Linux
Release	Windows August 20, 2022 Linux May 27, 2023
Genre(s)	First-person shooter
Mode(s)	Single-player

Entropy: Zero 2^[a] is a 2022 first-person shooter video game developed and published by Breadmen. It is a single-player modification for Half-Life 2 (2004) and is a sequel to Johnny "Breadman" Richardson's previous project, Entropy: Zero (2017). The game was released on Steam on August 20, 2022, as a free download for owners of Half-Life 2. A Linux version was also released on May 27, 2023.

The player assumes control of Aiden Walker, an "Elite" unit of the Combine's transhuman army who is tasked with capturing Dr. Judith Mossman, the former assistant of Earth's Administrator. As in the official Half-Life games, Entropy: Zero 2 tasks the player with navigating a series of levels, containing a mixture of combat, puzzle-solving, and scripted sequences. Additionally, the mod features several new gameplay mechanics, including new weapons and enemies, "portal" grenades, and drivable APCs.

Development on Entropy: Zero 2 began in 2018, and took over four years to complete. Key goals for the project during its development were to revitalize Half-Life 2's gunplay and overall combat flow and to create a character study of a "bad guy" within the confines of the Half-Life universe. Upon its release, Entropy: Zero 2 received positive reviews and went on to win Mod DB's 2022 "Mod of the Year" award in the "Players Choice" category.

Like the official entries in the Half-Life series, Entropy: Zero 2 is a single-player first-person shooter.^[1] In the game, the player assumes control of an "Elite" unit of the Combine's military,^[2] who is tasked with leading an assault on a rebel-held facility, located to the far-North of City 17.^[3] The player is tasked with navigating a series of levels, which are split into seven chapters and contain a mixture of combat, puzzle-solving, and scripted sequences.^[2][1] Featured locations include Nova Prospekt, a Combine prison that was partially destroyed during the events of Half-Life 2 (2004),^[4] and the central facilities of Arbeit Communications.^[5]

Entropy: Zero 2 includes several new gameplay mechanics, including new weapons, commandable Combine squadmates, drivable APCs, "portal" grenades that transport anything caught in their radius to the Xen dimension, new and returning enemies—including the "pit-drones" from Half-Life: Opposing Force (1999), and an optional companion character named Wilson.^[6][5][7] The game also features multiple endings, depending on several choices that the player has to make through its story.^[8] Additionally, Entropy: Zero 2 supports user-created mods and levels via the Steam Workshop.^[9]

Entropy: Zero 2 is set between the events of Half-Life 2 (2004) and Half-Life 2: Episode One (2006);^[10] in Half-Life 2, Gordon Freeman leads an uprising against an alien interdimensional empire known as the Combine, culminating in the destruction of the main reactor of the Citadel—the Combine's fortress on Earth—and the presumed death of Earth's Administrator, Dr. Wallace Breen.^[11] The game's story is told from the perspective of Aiden Walker (voiced by Sam "Trivvy" Pearson), an "Elite" unit of the Combine's military force.^[5][9] Prior to the Combine's invasion and subsequent occupation of Earth, Walker was employed as a prison guard in Arizona. Following his wife's death, Walker's daughter, Ava, was kidnapped by an unknown organization; Walker was implicated and subsequently imprisoned for the crime. After the onset of the resonance cascade at Black Mesa and humanity's failure to prevent the Combine from occupying Earth during the "Seven Hour War",^[b] Walker joined Civil Protection and quickly rose through its ranks, hoping that he would be eventually able to take advantage of the Combine's resources to find out who abducted Ava.^[12] Following his successful efforts to quell a rebel uprising in City 10, Walker was promoted to Elite status and his consciousness was uploaded to the Combine's data repository in order to serve as a template for the production of transhuman soldiers.^[13]

At Nova Prospekt, a Combine Advisor releases Walker from hibernation and assigns him to detain Breen's former assistant, Dr. Judith Mossman, who is searching for something in the Arctic with the aid of the rebels. Walker fights his way through Nova Prospekt's ruins, which have been overrun by Xenian "antlions", and boards a Combine dropship bound for the Arctic. Upon reaching the Arctic, Walker's dropship is shot down by the rebels and crash-lands near a research complex owned by Arbeit Communications. After Walker fights through multiple rebel squads, he is contacted by a clone of his consciousness, who has turned against the Combine. The clone tries to persuade Walker to abandon the Combine's mission, stating that Walker will be discarded after he accomplishes their tasks, but Walker refuses, prompting the clone to plunge him into the depths of the complex, which are crawling with headcrab zombies. With the assistance of a defective turret named Wilson, Walker dispatches the zombies; he also learns that Arbeit is connected to Aperture Science and a "project" that Arbeit and Aperture were involved in, which is now being sought after by both the rebels and the Combine. After reaching a surface elevator, Walker can choose to either take Wilson with him, or leave him behind; should Walker choose the former option, Wilson will express gratitude and request to be uploaded to Arbeit's main AI mainframe station.

Upon returning to the surface, Walker boards a Combine APC and travels to a second Arbeit facility, where he suspects that Mossman and her accomplices are located. At Arbeit #2, Walker and his Combine troops engage in a skirmish with the rebels, in which the rebels are neutralized and Mossman is captured. However, Walker's rogue clone reappears and attempts, but fails, to eliminate Walker and Mossman. After he hands Mossman over to the Combine, Walker is ordered by the Advisor to kill the clone, who is headed towards a third Arbeit facility. At Arbeit #3, Walker catches up to the clone, who is preparing to overload the facility's core. A firefight ensues between the two, in which the clone is wounded and forced to flee to Arbeit's primary excavation site—where the "project" is located. After stabilizing the core, Walker enters the excavation site, where he discovers that the "project" is the Borealis, a research vessel that vanished from the dry dock of Aperture's "Enrichment Center" prior to the Combine occupation of Earth.^[c] Walker finds the wounded clone, and the two discuss the vessel's value and what will happen to Walker should the Combine retrieve it. The clone asks Walker to end his life; regardless of his choice, the Advisor appears before Walker and crushes the clone's body, ensuring his death.

The Advisor states that Walker is to be rewarded for his accomplishments by becoming the "master template" for the transhuman Combine army. Should he submit to his "reward", Walker is stripped away of his memories and turned into an obedient slave of the Combine, which is killed by Freeman during a rebel assault on the Borealis. Otherwise, Walker kills the Advisor and destabilizes the facility's entropic control over the Borealis, plunging the vessel and Walker into a temporal event. Later, Walker awakens aboard the Borealis, where he is met by the G-Man. As remuneration for Walker's "exploits" with the vessel, the G-Man teleports Walker to the Combine's data repository and allows him to destroy the "imprint" used by the Advisors to clone him, but the G-Man states that he cannot bring back Ava. The G-Man prepares to put Walker in stasis, but before he can do so, the Combine—intent on recapturing the G-Man after he escaped from a high-security vault in City 17^[d]—locate the duo and attempt to capture them via a tractor beam; the G-Man escapes, but Walker is pulled into the beam. Afterwards, the Combine begin torturing Walker; if Walker chose to upload Wilson into Arbeit's AI mainframe, Wilson will release him from captivity. Arming himself with a prototype pulse rifle, Walker sets off to stop the Combine from reclaiming the Borealis.

Production on Entropy: Zero 2 began in 2018, following the release of its predecessor, Entropy: Zero (2017), and took over four years to complete. Unlike the first game, which was solely developed by Johnny "Breadman" Richardson, a development team, under the name Breadmen, was assembled by Richardson to help realize his vision for the game. An initial goal for the team was to rework the gunplay of Half-Life 2 (2004) and its overall "flow" of combat, as Richardson felt that the weapons in Half-Life 2 felt like "pea shooters". In addition to reworking the existing weapon arsenal, brand-new weapons, such as the "Xen" grenades, were also implemented; the Xen grenades were based on the "vortex" black hole grenades—a gameplay feature that Valve planned to include in Half-Life 2: Episode One (2006) but scrapped during the game's development.^[9]

Initial story drafts for Entropy: Zero 2 were set after the events of Half-Life 2: Episode Two (2007) and featured the protagonist of the first Entropy: Zero—named "Bad Cop"—being sent on a mission to retrieve an arming key from the ruins of City 17's Citadel and use it to open a new superportal to the Combine Overworld; these plans were scrapped in mid-2018, and the story of Entropy: Zero 2 was rewritten to sit more closely to the core narrative of Half-Life 2 and its sequel episodes.^[10] The finalized version of Entropy: Zero 2's story is also centered on Bad Cop, with the game revealing his real name to be Aiden Walker during a prologue sequence, titled "Chapter Zero".^[12]

A key goal for the development team when making Entropy: Zero 2 was to create a character study of a "bad guy" within the confines of the Half-Life universe. Unlike most of the official Half-Life games, which employ silent protagonists, Walker is presented as a fully-voiced, "reactive" character, with dynamic responses to various player actions within a level.^[9][10] When building out aspects of Walker's backstory, Richardson drew contrasting parallels to Half-Life series protagonist Gordon Freeman: both characters begin their respective lives as ordinary men, but whereas Freeman becomes a hero in his story, Walker turns into a "monster" with a deep hatred for humanity in his, which the Combine would seek to weaponize.^[10]

In Entropy: Zero 2's third chapter, Walker encounters a defective Aperture Science security turret, named Wilson, and is forced to carry him throughout the chapter in order to complete it.^[9] Wilson was initially conceptualized by Breadmen team member Caleb "CW3D" West as a companion to Walker that would provide comic relief during a "stressful" section of the game; but during development, the team decided to allow players to carry Wilson throughout the rest of Entropy: Zero 2, and players who choose to do so are rewarded with a unique sequence at the end of the game.^[9][10]

Entropy: Zero 2's score was composed by Spencer Baggett, who had previously contributed several music tracks to the first Entropy: Zero. Additional ambient music tracks for the mod were also written by Richardson and West.^[10] Baggett's original score was released to digital platforms on August 20, 2022.^[14] An extended soundtrack album, including both Baggett's tracks and the contributions made by Richardson and West, was published on Steam as a free digital download on September 14.^[15]

Entropy: Zero 2 was released on Steam on August 20, 2022, as a free download for owners of Half-Life 2.^[8] A version for the Linux operating system was released as part of an update on May 27, 2023, which also includes native controller support and Steam Deck compatibility.^[16]

Shortly after its release, NME reported that Entropy: Zero 2 received a "very positive" rating from players on Steam, with players giving praise to the game's new weapons, soundtrack, and its combat setpieces.^[8] In a feature for PC Gamer, Christopher Livingston stated that the mod was "inventive" and "surprising". Livingston also gave praise to the ability to assemble a squad of Combine soldiers, which he found to be "weirdly enjoyable", and complimented the game's main protagonist, who he felt was "pretty funny at times".^[4]

Entropy: Zero 2 won Mod DB's 2022 "Mod of the Year" award in the "Players Choice" category.^[17][18]

• Official website