Presented from the first-person perspective, the player can customize JC Denton's various abilities such as weapon skills or lockpicking, increasing his effectiveness in these areas; this opens up different avenues of exploration and methods of interacting with or manipulating other characters.

While the game contains eighteen different nano-augmentations, the player can install a maximum of nine, as each must be used on a certain part of the body: one in the arms, legs, eyes, and head; two underneath the skin; and three in the torso.

A USA Today reviewer found, "At the easiest difficulty setting, your character is puréed again and again by an onslaught of human and robotic terrorists until you learn the value of stealth.

"[7] However, through the game's role-playing systems, it is possible to develop a character's skills and augmentations to create a tank-like combat specialist with the ability to deal and absorb large amounts of damage.

Objectives can be completed in numerous ways, including stealth, sniping, heavy frontal assault, dialogue, or engineering and computer hacking.

Because of its scarcity, Ambrosia is available only to those deemed "vital to the social order", and finds its way primarily to government officials, military personnel, the rich and influential, scientists, and the intellectual elite.

With no hope for the common people of the world, riots occur worldwide, and some terrorist organizations have formed with the professed intent of assisting the downtrodden, among them the National Secessionist Forces (NSF) of the U.S. and a French group known as Silhouette.

[25] After completing his training, UNATCO agent JC Denton[26] takes several missions given by Director Joseph Manderley to track down members of the National Secessionist Forces (NSF) and their stolen shipments of the Ambrosia vaccine, the treatment for the Gray Death virus.

Manderley orders JC to fly to Hong Kong to eliminate Tracer Tong, a hacker whom Paul has contact with, and who can disable the kill switches.

Upon doing so, JC becomes a wanted man by UNATCO, and his kill switch is activated by Federal Emergency Management Agency (FEMA) Director Walton Simons.

Doing so, JC discovers that the corporation is the source for the Gray Death, and he can steal the plans for the virus and destroy the universal constructor (UC) that produces it.

JC meets with Illuminati leader Morgan Everett and learns that the technology behind the Gray Death was intended to be used for augmentation, but Majestic 12, led by trillionaire businessman and former Illuminatus Bob Page, stole and repurposed it.

After aiding the base personnel in repelling a Majestic 12 attack, JC meets X-51 leader Gary Savage, who reveals that Daedalus is an artificial intelligence (AI) borne out of the ECHELON program.

Page intercepts the transmission and targets a nuclear missile at Vandenberg to ensure that Area 51, now Majestic 12's headquarters, will be the only location in the world with an operational UC.

[29] Everett offers Denton the chance to return the Illuminati to power by killing Page and using the Area 51 technology to rule the world with an invisible hand.

After Looking Glass Technologies and Origin Systems released Ultima Underworld II: Labyrinth of Worlds in January 1993, producer Warren Spector began to plan Troubleshooter, the game that would become Deus Ex.

[33] After Spector and his team were laid off from Looking Glass, John Romero of Ion Storm offered him the chance to make his "dream game" without any restrictions.

[32] Noticing his wife's fascination with The X-Files, Spector connected the "real world, millennial weirdness, [and] conspiracy" topics on his mind and decided to make a game about them that would appeal to a broad audience.

[41] Spector later concluded that the team was "blinded by promises of complete creative freedom", and by their belief that the game would have no budget, marketing, or time restraints.

[43] Spector felt that the best aspects of Deus Ex's development were the "high-level vision" and length of preproduction, flexibility within the project, testable "proto-missions", and the Unreal Engine 1 license.

[44] The team's pitfalls included the management structure, unrealistic goals, underestimating risks with artificial intelligence, their handling of proto-missions, and weakened morale from bad press.

[37] Though Spector originally pictured Deus Ex as akin to The X-Files, lead writer Sheldon Pacotti felt that it ended up more like James Bond.

[51] A year later, the team reached a milestone for finished game systems, which led to better estimates for their future mission work and the reduction of the 500-page design document to 270 pages.

[42] The soundtrack of Deus Ex, composed by Alexander Brandon (primary contributor, including main theme), Dan Gardopée ("Naval Base" and "Vandenberg"), Michiel van den Bos ("UNATCO", "Lebedev's Airfield", "Airfield Action", "DuClare Chateau", plus minor contribution to some of Brandon's tracks), and Reeves Gabrels ("NYC Bar"),[57] was praised by critics for complementing the gritty atmosphere predominant throughout the game with melodious and ambient music incorporated from a number of genres, including techno, jazz, and classical.

A PlayStation 2 port of the game, retitled Deus Ex: The Conspiracy outside of Europe, was released in 2002 in North America on March 26,[66] in the United Kingdom on June 7,[67] and in Australia on December 13.

[68] and Along with motion-captured character animations and pre-rendered introductory and ending cinematics that replaced the original versions, it features a simplified interface with optional auto-aim.

[74][75] Though their quality assurance did not see major Direct3D issues, players noted "dramatic slowdowns" immediately following the launch, and the team did not understand the "black box" of the Unreal engine well enough to make it do exactly what they needed.

[86] The Lay D Denton Project, a mod adding the ability to play as a female JC – a feature that had been planned for Deus Ex but ultimately not implemented – was released in 2021.

[114] He poked fun at JC's "Joe Friday, 'just the facts', deadpan", and the "truly cheesy accents" of minor characters in Hong Kong and New York City.

IGN called the graphics "blocky", adding that "the animation is stiff, and the dithering is just plain awful in some spots", referring to the limited capabilities of the Unreal Engine used to design the game.