Mages Inc. Announces Juggernaut, a Nearly Fully AI-Generated Retro FPS From the Makers of Steins;Gate

Mages Inc., the Tokyo studio best known for the Science Adventure visual novels — including Steins;Gate and its August 2026 remake Steins;Gate Re:Boot — has announced Juggernaut, a free-to-play retro first-person shooter whose own Steam page discloses that 100 percent of its source code and effects, 60 percent of its graphics and 50 percent of its sound were generated with generative AI. The game's store listing went live on September 10, 2026, ahead of an unannounced release date.

Juggernaut is structured as a shareware-style boomer shooter in the vein of late-1990s Wolfenstein-engine titles: the player has to clear 5,000 zombies across flat, pixellated arenas across multiple modes. A second paid product, the Juggernaut Assets Maker, ships alongside the base game as a level editor with the same disclosure ("the source code for this application was generated using generative AI") and is being marketed to players who want to "make it more Japanese" or "make it sexier" by swapping in custom art. Both products carry an AI Disclosure block on Steam under the labels "Source code: 100%", "Graphics: 60%", "Sound: 50%" and "Effects: 100%."

The shift in studio direction is sharp. Mages has spent two decades on visual novels — Steins;Gate alone holds close to 6,000 "overwhelmingly positive" reviews on Steam — and its only previous action-game credit is a Japan-only Xbox 360 release. Kotaku, PC Gamer and news-aggregator coverage framed the announcement as "vibe-coded," leaning on the fact that the company's own disclosure labels the project as almost entirely machine-written. Steam's user-base response has been notably hostile, with multiple threads quoting "if you don't care enough to make a game why should I care enough to buy it" in response to the store listing.

The timing is awkward for the studio. Juggernaut surfaces roughly six weeks after Steins;Gate Re:Boot, a faithful remake that has accumulated close to 600 "very positive" Steam reviews since its August 20 launch, and during a wider industry conversation about AI-disclosure quality on the Steam store. Mages' transparency on percentage splits is unusually granular — many AI-disclosure entries on Steam are vague or absent — which makes the project a clear case study in how generative AI disclosure interacts with established back catalogs.

The base game is positioned as free-to-play; the level editor is the paid component, and pricing has not been confirmed. No platforms other than PC have been announced, and no release date has been set. Wishlisting is open now, with the Juggernaut store page on Steam carrying the full AI Disclosure breakdown and the official Juggernaut Assets Maker DLC listing on the same product entry.