View source for Half-Life: Cross Product

{{ModStatus|status=released|size=big|engine=Goldsource|download=https://store.steampowered.com/app/3416640}}

{{Game Infobox
| title = Half-Life: Cross Product
| image = CrossProduct cover.png
| developer = [[The Phoenix Project Software]]
| publisher = [[The Phoenix Project Software]]
| releasedates = April 5, 2020 '''(ModDB Multiplayer early access release)''' <br> August 22, 2025 '''(Steam Multiplayer release)'''
| genre = {{w|icon=0|First-person shooter|First-person shooter}}
| mode =  {{w|icon=0|Multiplayer video game|Multiplayer}}
| platform =  {{w|icon=0|Windows|Windows}}, {{w|icon=0|Linux|Linux}}
| engine = {{gldsrc|4}}
| appid = 3416640
| codelang =  {{w|icon=0|C++|C++}}
| modsupport = Yes, [[Steam Workshop]] '''(see {{Harbinger|4}})'''
| sdk = {{Aura|4}} SDK

| steamdeck = {{Steamdeck unknown|4}}
| distribution = [[Steam]]
| links = {{Steam store|app/3416640|'''Steam''' page}}
}}

{{Cross Product|4}} is an upcoming first-person shooter game developed and published by The Phoenix Project Software based on Valve's {{hl|4}}. Set in an alternate-history sci-fi universe, it builds on the foundations of ''Half-Life'' with a rich dystopian world, experimental game mechanics, and a narrative, with all elements inspired by other games and films.

''Cross Product'' is both a narrative-driven singleplayer experience, and a multiplayer online arena shooter. It started development in 2018 with the '''multiplayer component''', aptly named '''''Half-Life: Cross Product Multiplayer''''', having released on April 5, 2020 and a Steam Release on August 22, 2025 after it was announced two months prior. In 2021, The Phoenix Project Software introduced the {{Aura|4}} framework (a fork of {{ag|4}}) to Multiplayer, and since August of that year, it has seen yearly "Season" updates, introduced to streamline development of the game.

Notable features of the multiplayer, upon ''Half-Life Deathmatch'', include a varied set of switchable gamemodes, a large amount of maps, extensively customizable settings such as '''field-of-view (FOV)''', [[Steam Workshop]] support, and the game promotes advanced movement features & techniques such as bunny-hopping for competitive play.

==Story overview==
As the game has yet to be released, limited information regarding the story has been revealed publicly. Early prototype demos were released in 2020 which suggested the player plays as protagonist "Zeke", as fragments of the Black Mesa Research Facility began popping up in his universe. Over the years, development of the game has evolved, and the story has changed dramatically.

''Cross Product'' takes place in a fractured alternate-universe upon a world shaped by a catastrophic event known as the Alexandria Incident, which unleashed a deadly mutagenic virus in the country of Aethoron. Set in 1999, five years following the incident, players follow protagonist '''Zeke Jackson''', a former Aethoric Army Marine, as he navigates the quarantined region, and the city of New Roma, battling intelligent infected and searching survivors to seek a definitive escape.

==Game structure==
===Singleplayer campaign===
''Cross Product'''s main area of development since 2020 has been its campaign. In 2023, it was announced that it would be released in a "split layout" of parts, starting with '''''Part I: Grave.'''''

===Multiplayer===
''Cross Product Multiplayer'' was released to Early Access in 2020 and then on [[Steam]] in 2025, and is built on the Aura framework. Multiplayer in ''Cross Product'' includes:
* Team-based and free-for-all modes
* An extensive collection of maps
* Steam Workshop support for maps, gamemodes, and more
* Extensive customization
* [[Steam Achievements]]
* Routine updates

==Development==
===Inception - Zombies Ate My Neighbors: GoldSrc Edition & creaTive Deathmatch (2018-2019)===
In late 2018, The Phoenix Project Software (then-known as "Killer Studios") revealed a project on [[ModDB]] called ''Zombies Ate My Neighbors: GoldSrc Edition'' which was to be a remake of the 1994 top-down 2D shooter from a first-person perspective on the [[GoldSrc]] engine. A prototype demo was released, featuring a character model of the game's original protagonist, and a recreation of the first level. The 2018 demo boasted the codename "zamnhl" which has since become the official internal codename and abbreviation for the game.

Later, in May 2019, The Phoenix Project Software announced another Mod in the making, this time a multiplayer arena shooter, called ''creaTive Deathmatch''. No special or innovative features were revealed at the time.

===Grey Source & Shooter Tourneys (2019-2020)===
In November 2019, The Phoenix Project Software, while working on the [[Grey Source]] codebase, rebooted the ''creaTive Deathmatch'' project by forking an open-source mod by Martin Webrant called Adrenaline Gamer. This decision was made due to the fact that AG already had good skill-based gameplay support such as wallgaussing and bunny-hopping, and it had a gamemode & gametype system, with strong potential for expansion and adaptation.

After nearly a year in development, "Public Playtest" (PPT) builds of the game began popping up on The Phoenix Project Software's GitHub page, under the name ''Shooter Tourneys''.

===Half-Life: Zombies Ate My Neighbours announcement & Shooter Tourneys release (2020)===
In February 2020, the former ''Zombies Ate My Neighbours: GoldSrc Edition'' ModDB page was rebranded to ''Half-Life: Zombies Ate My Neighbours''. It was announced that instead of a remake, the game would become a cross-over.

In March it was announced that alongside the eventual release of ''Half-Life: Zombies Ate My Neighbours'', ''Shooter Tourneys'' would be bundled alongside it as the multiplayer component.

Later, ''Shooter Tourneys'' version 1.0 was officially released on April 15, 2020. As an effect of the announcement shortly beforehand, "zamnhlmp" became its codename.

===Further development & demos (2020)===
Throughout 2020 and during the COVID-19 pandemic, The Phoenix Project Software proceeded with early development on the game and its Grey Source codebase. The company slated the title for release on November 21, 2020 as it remained a "simple crossover mod." A demo was released on April 30, 2020, featuring campaign maps leading up to Zeke's transport to the Half-Life world.

In October that year, an article was published covering development updates and that the game would be "hopefully releasing" in 2021, with two new trailers created boasting the tagline "Two Worlds, One Man."

===Multiplayer early access release (2021)===
In February 2021, ''Shooter Tourneys'' received its Version 2.0 update where the game was renamed to ''Half-Life: Zombies Ate My Neighbours Multiplayer''. Since then it has been considered an Early Access title which The Phoenix Project Software refers to as a "good dumping ground for testing gameplay features and weapons etc, and a good way for players to provide feedback on the game which will influence our decisions made for the campaign."

===Aura & seasons (2021-2022)===
In May 2021, The Phoenix Project Software released Multiplayer version 2.4, featuring the new '''Aura''' framework. Prior to this update, it had used the original codebase which had started back in 2019, but according to lead developer Sabian Roberts in a 2025 retrospective, the old codebase "was a mess. I didn't know how to organize code back then so the whole thing was a mess and there was all sort of things I tried adding which I never removed, so it started breaking other things, and eventually there was too much technical debt to consider it fixable, and I also wanted to catch the project up with Adrenaline Gamer's upstream changes. It was just easier to restart it from scratch."

The Phoenix Project Software named the game's codebase separately to keep it open for other modders and developers to use it and its features for other multiplayer {{gldsrc|4}} games, and TPPS itself had desires to use it for other title of their own.

Later that year, in July, the Seasonal Scheme was announced, starting with '''''Season 6: HECU'''' in the version 2.6 update, released on August 28, 2021. It became a way for TPPS to "streamline development of the game to help us focus on our other projects in the meantime."

The following year, in 2022, '''''Season 7: Black Ops (v2.7)''''' was released.

===Story updates & Seasons 8-9 (2022-2024)===
In late 2022, after the release of '''''Season 7: Black Ops''''', development of the next update was initiated, slated for released in Q3 2023, under the working title "Season 8: Legends of New Roma." In contrast to its predecessors, Season 8's name was of a new, original topic.

Nearly a year later in October 2023, an article was published confirming that development of the game's campaign had been restarted from scratch and that the story had received a rewrite. The article also revealed details of the new story such as the city New Roma, and that the game would be produced & released in parts, though the number of parts has been reduced from 5 to 3.

In December 2023, '''''Season 8: Black Mesa Inbound (v2.8)''''' was released for Multiplayer as a tie-in to the 25th Anniversary of Half-Life.

During early 2024, The Phoenix Project Software took a hiatus due to lead developer Sabian Roberts' focuses on his academia, though development of the Season 9 update was still initiated in the Spring. The company returned to full work in August and in September, '''''Season 9: White Sands (v2.9)''''' was announced. Season 9 focused more on "quality-of-life" fixes rather than all-new content and features, and TPPS called it the "biggest Quality of Life Update ZAMNHLMP has ever received," though it is not completely lacking on new content as it still added two new gamemodes, a soundtrack, and a new map. It was released in November 2024, with a holiday themed patch named '''''Season 9 Patch I (v2.9.1)''''' following it in December.

===Rename to Cross Product and the Steam release of Multiplayer (2025-)===
In late 2024, The Phoenix Project Software purchased access to Steamworks, and used their other project, [[Half-Life Legacy]], as a test for the platform.

During the following months of early 2025, development of the Season 10 update was initiated and later on in the spring, it was announced that due to internal developments made, the game was be officially renaming to ''Half-Life: Cross Product.''

The following month, in June 2025, The Phoenix Project Software revealed that, in its Season 9 state, ''Half-Life: Cross Product Multiplayer'' would be releasing on Steam that summer. To mark the occasion, TPPS also developed '''''Season 9 Patch II (v2.9.2)''''' and launched a Closed Beta Program where players could sign-up and test the game's update early, which added [[VGUI2]] support, Steam Workshop, and more.

''Half-Life: Cross Product Multiplayer'' was released on Steam on August 22, 2025.