A video game genre characterized by simulation-driven game worlds and a high level of player agency.
The "immersive sim" is a video game genre that existed in some form since The '90s, codified primarily by Looking Glass Studios and Ion Storm Austin (the term itself was coined in 2000 by LGS's Warren Spector, the grandfather of the genre) , but has experienced a major comeback in The New '10s. Games in this genre aim to simulate a large believable lived-in space (where the players' avatar exists as an active entity, unlike in Strategy Games) through the use of clever game systems and advanced artificial intelligence, as well as to enable maximum player expression while refusing to hold their hand. Immersive sims commonly have following traits (the list is neither normative, nor exhaustive):
- High level of player agency. Players are thrown into the virtual space and given goals to achieve and tools to use, but no predetermined paths to follow. Instead, they are expected to explore and to find the best way to reach their goal in a manner that best suits their current tactics and playstyle, relying on creativity and improvisation instead of finding the "correct" solution. The designers may offer some entry points and starting suggestions, in order to avoid overwhelming the players, but these are never rigid paths to be followed for the rest of the level (or even the game).
- High systemicity. The game is governed by global rules (such as the Physics Engine), properties, and mechanics that work consistently throughout, with minimal use of systemic exceptions like scripted events, one-off animations, and cutscene set pieces. Immersive sims also tend to recycle previously introduced elements and obstacles in different contexts.
- Emergence. Interactions between various game subsystems facilitate emergent combinations thereof that the developers did not explicitly code into the game. Combined with high player agency, this also enables the Unexpectedly Realistic Gameplay characteristic of the genre.
- Consistency. As noted above, special cases and one-offs are generally few and far in-between: e.g. there are no Invisible Walls and no Gameplay Ally Immortality — but even if an important NPC bites the dust, there is no Game Over, and the simulation just carries on. In fact, player character's death is often the only explicit failure state.
- High reactivity. The game world reacts to the player's actions and observably evolves over time. Story Branching often occurs not via explicit (dialogue) choices, but through gameplay actions, including ones that may appear like Sequence Breaking at first.
Games in this genre include:
- Arx Fatalis (2002, Arkane), intended as a Spiritual Successor to Ultima Underworld, is likewise set in a giant underground cavern populated by a simulated Fantasy Kitchen Sink of various creatures. The player character's task is to find a way to prevent the arrival of a God of Evil by manipulating the game systems to obtain a weapon strong enough to banish him. Notably, there is no dialogue system, and the player instead makes Story Branching choices, including different quest resolutions exclusively through in-game actions.
- BioShock (2007, Irrational) sees the player trapped in an underwater city of Rapture, once utopian, but now fallen to anarchy and civil war. It features a simulated ecosystem of splicers, Big Daddies, and Little Sisters, and although split into distinct areas, they can still be traversed in many ways and most previous ones remain accessible (although there is rarely any point in returning).
- BioShock 2 (2010, 2K Marin) returns to Rapture, although a decade into the future and even more decrepit.
- BioShock Infinite, on the other hand, is generally not considered part of the genre, due to its extremely linear level progression and heavy emphasis on First-Person Shooter mechanics. Its two-part DLC Burial at Sea, however, was a deliberate return both to Rapture and to the immersive sim mechanics of the previous two games (part two even includes a challenge "1998 Mode" as a throwback to the original Thief).
- Deus Ex (2000, Ion Storm Austin) is considered one of the two great Trope Codifiers of the genre (alongside System Shock), and the game Warren Spector is most proud of. Set in a Cyberpunk, Conspiracy Kitchen Sink future, the game follows the Thief model of distinct missions and simulated level hubs, but allows the player character JC Denton navigate them in any way and sequence imaginable. It was also one of the earliest games to make action-based and stealth-based walkthroughs equally viable, gameplay-wise.
- Deus Ex: Invisible War (2003, Ion Storm Austin) had improved upon the original's story and game world reactivity, but shipped with a much weaker enemy AI and simplified game systems, which both contributed to the game's poor reception (with the good AI and interlocking game sub-systems being two of the hallmarks of good immersive sims).
- Deus Ex: Human Revolution (2011, Eidos Montreal) had streamlined the first game's formula, albeit still allowing for emergent gameplay (such as hacking a automatic turret and hauling it to the boss arena). It also features several Deadly Shadows-like hub levels from which the main story missions can be accessed.
- Deus Ex: Mankind Divided (2016, Eidos Montreal) improved upon the Human Revolution immersive mechanics, particularly in its central hub level of the futuristic Prague, as well as adding more options to tackle in-game challenges and affect different outcomes.
- Dishonored (2012, Arkane) is set in the plague-stricken city of Dunwall and follows the Thief model of levels clearly separated by mission, with each level simulating the behavior of city guards, civilians, zombie-like weepers, and wildlife (e.g. rats). Unlike in Thief, the player character Corvo Attano may use both stealth, and open violence, or any combination of the two to achieve to assassinate (or otherwise put out of commission) his marks. The Knife of Dunwall and Brigmore Witches DLC duology starring the assassin Daud follows the same model, at one point even simulating an all-out Mob War between two Dunwall gangs.
- Pathologic (2005, Ice-Pick Lodge) is set in an unnamed stepped town ravaged by a mysterious epidemic, and the player steers one of three variously eccentric characters in an attempt to find a cure. Notably, the game runs in actual Real Time and always ends after 12 in-universe days, and it is entirely possible to miss the vast majority of the story events unless you know exactly when and where the next one will occur.
- Prey (2017, Arkane) strongly resembles System Shock in that it is set on an abandoned Talos I space station overrun by the alien Typhon. The station is one continuous interconnected zone, inhabited by a variety of Typhon creatures and a handful of human survivors, including the player character Morgan Yu.
- S.T.A.L.K.E.R. (2007, GSC Game World) is set in the vast Zone of Exclusion surrounding the Chernobyl nuclear power plant, which, in this setting, spawned a large number of bizarre anomalies and mutants. The player character is a "stalker" (a professional Zone trespasser) who is tasked with "killing Strelok" and must navigate the simulated environment and ecosystem of the Zone to find out who Strelok is and why he must die.
- System Shock (1994, Looking Glass) is often listed as one of the two great Trope Codifiers of the genre (alongside Deus Ex), being Looking Glass' first original project. Its setting, the Citadel space station, is a single multi-layer zone controlled by the malevolent AI with a god complex and populated by robots, cyborgs, and mutants it controls. Among other things, System Shock introduced to the genre and popularized the After the End settings (often involving epidemics and/or societal collapse, thus justifying even the most extreme styles of play) with few speaking NPCs and Apocalyptic Logs as main means of storytelling.
- System Shock 2 (1999, Irrational) is set some time after the first game on two docked spaceships, the Von Braun and the Rickenbacker, after both have been overrun by the mutagenic alien hive mind known as "the Many".
- System Shock 3 (TBA, OtherSide) is currently in development, with Warren Spector at the helm, and promises to be true to its predecessors' principles.
- Thief: The Dark Project (1998, Looking Glass) is remembered primarily as one of the early success stories of the Stealth-Based Game, because of its heavy emphasis on avoiding detection, but the sneaking itself was very much based in emergent problem-solving within a largely-unscripted game world (one particular innovation was the intricate simulation of light, shadows, and noise). It was also the first entry in the genre to ditch the "single interconnected world" model in favor of smaller sequential levels, each representing a location within a much larger (nameless) City.
- Thief II: The Metal Age (2000, Looking Glass) scaled down the fantasy elements of the first game, such as non-human monsters and maze-like dungeons, in favor of making the City seem like a realistic urban environment. It also expanded the protagonist Garret's toolset with additional technological tools.
- Thief: Deadly Shadows (2004, Ion Storm Austin) introduced to the series the central hub level, consisting of several districts of the City, from which the plot mission locations are accessed and which are unlocked for exploration gradually as the story progresses. This has also closed the last immersion-breaking gap of the previous games, transforming the shopping screens between their missions into a in-universe interaction.
- The 2014 reboot by Eidos Montreal, however, is not considered part of the genre anymore, for much the same reasons as BioShock Infinite: a much more linear level traversal (reducing the exploration element), reliance of scripted events, reactive AI, and a smaller, yet more specialized toolset to overcome challenges. One change that is often cited to illustrate the difference between simulated and scripted world is that the rope arrows in the new Thief can only be attached to hotspots placed by the level designers, rather than to any wooden surface, like in the older games.
- Ultima Underworld: The Stygian Abyss (1992, Looking Glass) is usually named as the Ur-Example of the genre. A Spin-Off of the Ultima, it put the recurring dungeon of the Stygian Abyss into the focus, simulating its massive and complex multi-level ecosystem in real time. The series' overarching Player Character, the Avatar, found himself thrown into the Abyss with an overarching task to free a kidnapped damsel from a powerful demon but no obvious path towards it, requiring the player to try out different strategies and to improvise. Warren Spector's inspiration for this emergent approach to in-game problem solving came from Dungeons & Dragons and from watching a playtester solve an Unwinnable by Mistake puzzle in Ultima VI by exploiting the fact that his animal companion Sherry the Mouse could squeeze under a locked door and open it from the other side. Lessons learned from this game influenced both Ultima Underworld II: Labyrinth of Worlds (1993, Looking Glass) and Ultima VII to a considerable degree.
- Underworld Ascendant (TBR, OtherSide) is a Kickstarted Spiritual Successor to Ultima Underworld (would be a sequel if not for trademark issues) developed by many of the same people. It will likewise simulate the Stygian Abyss as a massive underground ecosystem and society, and the developers are working on what they call the "Improvisation Engine" to make sure players always have several ways to reach their goals.
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