Unlike other first-person games of the time, System Shock features true 3D environments, allowing the player to look up and down, climb, duck, jump, and lean to the side. Critics praised System Shock and hailed the game as a major innovation in its genre. It was later placed on multiple hall of fame lists. Despite its technological feats and critical acceptance, System Shock was outsold by its contemporaries. A sequel, System Shock 2, was released by Looking Glass Studios and off-shoot developer Irrational Games in 1999.
After hacking SHODAN, removing the AI's ethical constraints, and handing control over to Diego, the protagonist undergoes a surgery that fits him with the promised neural interface. Following the operation, the hacker is put into a six-month controlled healing coma. The game begins as the protagonist awakens from his coma, finding that SHODAN has commandeered the station. All robots aboard have been reprogrammed for hostility, and the crew have been either transformed into cyborgs and mutants or killed.
Rebecca Lansing, a TriOptimum counter-terrorism consultant, contacts the player and claims that Citadel Station's mining laser is being charged up for a strike against Earth. Rebecca informs the hacker that a certain crew member should know how to deactivate the laser, and promises to remove record of the hacker's incriminating exchange with Diego provided the strike is stopped. SHODAN plans to destroy all major cities on Earth in a bid to become a kind of god. Through information gained from log discs, the hacker discovers that firing the laser into Citadel Station's own shields will destroy it. Foiled by the hacker's work, SHODAN prepares to seed Earth with a mutagen virus — the same one responsible for turning the station's crew into mutants. The hacker again defeats the AI by jettisoning the chambers used to cultivate the virus.
Next, SHODAN begins an attempt to download itself into Earth's computer networks. Following Rebecca's advice, the hacker destroys the four antennae used by SHODAN to prevent the download's fulfillment. Soon after, Rebecca contacts the hacker, revealing that she has convinced TriOptimum to authorize the station's destruction — and giving him details on how to destroy it. After obtaining the necessary codes, the hacker begins the station's self-destruction sequence, and escapes to the life pods.
There, the hacker finds Diego, transformed into a powerful cyborg by SHODAN to guard the pods. The hacker quickly dispatches him and attempts to disembark. However, SHODAN prevents the pod from launching in an attempt to force the player to remain on the station while the bridge — containing SHODAN — is jettisoned to a safe distance. Rebecca tells the hacker that he can still survive if he reaches the bridge; SHODAN then intercepts and jams the transmission. The hacker is still able to find his way to the bridge as it is released from the main station, which soon detonates. The hacker is then contacted by a technician who managed to circumvent SHODAN's jamming signal. The technician informs the hacker that the only path to defeating SHODAN lies in cyberspace, due to powerful physical shields protecting the computers. Using a terminal near SHODAN's mainframe, the hacker enters cyberspace and destroys SHODAN. After his rescue, the hacker is offered a job at TriOptimum, but declines in favor of continuing his life as a hacker.
System Shock features an interface similar to that of Ultima Underworld, with a free moving mouse cursor for aiming, manipulating objects, and using the heads-up display. This interface is also used for leaning left or right, looking up and down, crouching and crawling. An inventory on the heads-up display stores items and weapons.
The game contains various dermal patches, each with certain effects, and occasionally negative after-effects. A "Medipatch" gradually restores a small amount of the player character's health, while a "Berserk" patch increases the power of the player character's mêlée attacks — but causes hallucinations as a side-effect.
Throughout System Shock, players find attachable hardware for the protagonist's neural implant, including targeting systems, energy shields and head-mounted lanterns. One piece of hardware plays log discs and e-mails, which provide the player with hints, and helps advance the story. Increasingly advanced versions of hardware are found as the game continues. Most active hardware gradually drains energy from a main reserve, necessitating economization.
The player may temporarily enter Cyberspace through specific terminals in System Shock. While in Cyberspace, the player is able to move weightlessly through a wire frame 3D environment, collecting data and fighting security programs. Actions in Cyberspace sometimes cause events in the game's physical world — for example, certain locked doors may only be opened from Cyberspace.
The game features sixteen weapons, of which the player can carry a maximum of eight at once. Projectile weapons often have multiple, selectable ammunition types; certain munitions are more powerful than others. Energy weapons forgo ammunition, instead drawing from the player's energy supply. These weapons feature adjustable shot power, which proportionally affects energy consumption. If fired too often, energy weapons will overheat, making them unusable for a short time. Several types of explosives may also be found, ranging from percussion grenades to land mines and adjustable time bombs.
Weapons and munitions deal certain kinds of damage, and enemies are sometimes immune or more vulnerable to particular types of damage. For example, electromagnetic pulse weapons heavily damage robots but do not affect mutants. Conversely, gas grenades are effective against mutants, but do not damage robots. If an enemy is hit by an attack to which it is not immune, the damage calculation is modified by factors including armor absorption, vulnerabilities, critical hits, and a degree of randomness. These effects are presented as messages such as "Normal damage", displayed near attacked enemies when certain hardware is active.
Developer Seamus Blackley designed an advanced physics system for the game, using an invisible 3D model to govern the player character's physics in real-time. Lead designer Doug Church stated that the system effected "the head tilt[ing] forward when you start to run, and jerk[ing] back a bit when you stop", and that "when you run into a wall, or are hit by a bullet, or run into by an enemy, your head is knocked in the direction opposite the hit, with proportion to mass and velocity of the objects involved." The physics system also allowed wall-climbing.
Prior to System Shock's release, Doug Church stated that "we've always felt that first person games are maximally atmospheric", and "in System Shock we are pushing that in as many ways as we can." Developers focused on the game's story to achieve their desired atmosphere; Looking Glass Technologies believed that "things have to look real ... [and] feel real". Similarly, the game's log and e-mail messages were designed to be "more than 'you must pull lever N'", with the goal of "[making] them feel as though they came from and are going to someone real." As no non-player characters appeared in System Shock to converse with the player, the plot was conveyed through these log discs and e-mails. System Shock 2 developer Johnathan Chey later stated that this decision resulted from 1994's computer technology being "simply inadequate to support believable and enjoyable interactions with [non-player characters]."
System Shock was released on floppy disk for DOS in March 1994, with no speech and support for only a 320x240 display resolution. An enhanced CD-ROM version was released in November 1994, featuring full speech for logs and e-mails, multiple display resolutions (up to 640x480), and more detailed graphics. Unsurprisingly, the CD-ROM version is often cited as superior. The game was also released for the Apple Macintosh at this time. In an interview with GameSpy, System Shock producer Warren Spector expressed regret concerning the floppy version, stating, "I wish I could go back and make the decision not to ship the floppy version months before the full-speech CD version. The additional audio added so much it might as well have been a different game. The CD version seemed so much more, well, modern. And the perception of Shock was cemented in the press and in people's minds by the floppy version (the silent movie version!). I really think that cost us sales..."
Games Domain was impressed by the game's plot and visuals, but criticized the CD-ROM edition's SVGA support, calling the performance "hideous even on [the recommended system]". GameBytes also found the game to be a "technical marvel", though at a cost in performance.
Computer Gaming World awarded the game 4½ stars out of 5, praising its scale, physics system and true 3D environments, and extolling the presentation of Cyberspace as "nothing short of phenomenal". The magazine felt negatively concerning the "little sense of urgency" and "confusing level layouts". Next Generation Magazine summarized the game as "... a great blend of strategy and action backed up with all the extras", granting it four out of five stars.
Certain game developers have acknowledged System Shock's influence on their products. With Deus Ex, developer Warren Spector revealed a desire to "build on the foundation laid by the Looking Glass guys in games like ... System Shock." Developer Ken Levine has commented that the "spirit of System Shock is player-powered gameplay: the spirit of letting the player drive the game, not the game designer", and at Irrational Games "... that's always the game we ideally want to make."
In the years following its release, System Shock has been inducted into many "hall of fame" lists, including those by PC Gamer, GameSpy and Computer Gaming World. A sequel to System Shock, entitled System Shock 2, was released in 1999 to further acclaim and award, bringing back SHODAN and taking place forty-two years after the first.