Taking Apart Stealth

Games are composed of rules. One of the goals of the game designer is to create sets of rules that work together in order to create dynamic and deep gameplay. This means gameplay with many possible non-redundant outcomes, strategies, or states, where the player is capable of planning around each element of the design and the design also attempts to thwart the player while opening up more ways for the player to interact with the design and overcome it.

This is a deconstruction of the basic elements of stealth games, arranged in an order of basic complexity up to high complexity. Each level is the number of discrete elements present. These elements are all listed at the end. A game with 12 of these elements could be said to be a, “level 12 stealth game” (though of course this is an arbitrary scheme and shouldn’t be taken as a definitive statement on a game’s quality). The early levels are mostly linear in their progression, building on each other in what I feel is a natural order of progression. Later levels are ordered more or less arbitrarily, as those elements are not really a part of the core stealth experience, but are supplemental, and frequently combined in different ways across games. In general, the core concept of stealth games is enemy units not having an automatic or universal awareness of the player’s location and the manipulation of enemy hostilities and behaviors at a distance.

2013-12-15_00047

Level design in particular is also a huge part of stealth games, and can range from guard placement, patrols, and environmental features. The lack of many of these elements can be compensated for with good level design, such as making unchanging guard patrols extend far through the level, and having the level be fairly open so guards sweep every area. This can allow guards to detect the bodies of downed guards, which they would never see in a game where their patrol pattern didn’t overlap where the guard was taken out. Adding different combinations of lighting and sound-producing floor surfaces in a level can dramatically change an encounter with even simpler AI types. There are many more ways to use level design in stealth games to create interesting possibilities, but that is unfortunately not the focus of this article.

In a stealth game, the goal of good AI is not just to be hard, but to challenge the player in a way that brings out variation and requires the player to think to succeed, usually by countering one of the player’s options or strategies. In order to do that, each of these levels imposes upon the player another distinct AI strategy they must deal with, but also gives them a means to gain an advantage over their enemies. For AI in general to improve, this type of discrete behavioral method and game design philosophy is what will have to be employed. Good AI is built on many distinct parts working well together, and good game design is built on challenging the player in a way that opens up variation while also forcing them to play well.

This list serves as a mirror for what it means to improve a game’s artificial intelligence, and on a broader level, what it means to improve a game’s challenges. Games exist as challenges because we enjoy being challenged. The quality of the challenge isn’t just that it’s hard, but in the particular methods by which it is hard. This is best expressed by the term “Depth.” The definition of depth I use is the range of different possible differentiated scenarios that can occur in a game related to succeeding or failing. Difficulty creates depth by differentiating scenarios from one another. You don’t win by just doing anything in a difficult game. You have to do the right things at the right times to succeed. Too much difficulty can limit depth, making the game a process of memorization and execution.

Each entry in the list will recite all the previous entries, with modifications in bold.

2013-08-08_00008

  • Level 1: Guards are in fixed positions. If they see you, they attack you until you are dead or they are disabled.
Featured in: Nearly all games, definitely all stealth games.
  • Level 2: Guards move around in fixed patrols. If they see you, they attack you until you are dead or they are disabled.
Featured in: Same.
  • Level 3: Guards move around in fixed patrols. If they see you, they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing, but will remain in position around that area until a timer runs out then return to their original patrols
Featured in: Thief (2014), Dishonored (both AIs had a habit of standing around looking dumb)
  • Level 4: Guards move around in fixed patrols. If they see you, they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they return to their original patrols
Featured in: Metal Gear Solid, Thief, Mark of the Ninja, most stealth games.
  • Level 5: Guards move around in fixed patrols. If they see you, they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they return to their original patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look at the source of the disturbance.
Featured in: Thief (2014), Dishonored (again, tendency to stand around)
  • Level 6: Guards move around in fixed patrols. If they see you, they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to their original patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance.
Featured in: Metal Gear Solid 2 and beyond, Thief 2, Mark of the Ninja, most stealth games

2013-06-12_00007

  • Level 7: Guards move around in fixed patrols. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to their original patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance.
Featured in: Most stealth games have detection based on distance, and to some degree lighting.
  • Level 8: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance.
Featured in: Games with this feature are rare, I cannot name any. Deus Ex Human Revolution had alerted guards return to changed patrols in some circumstances.
  • Level 9: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time.
Featured in: Metal Gear Solid 2 and 3, Monaco, Hitman.
  • Level 10: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase.
Featured in: Thief, Metal Gear Solid 2 onward, Mark of the Ninja, Monaco, Hitman, and most others (amusingly, not the original deus ex)
  • Level 11: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. The bodies of guards can be moved from their locations.
Featured in: Dishonored, Thief, Metal Gear Solid 2 and 3, Deus Ex, Mark of the Ninja,
  • Level 12: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards.
Featured in: Was going to be featured in Dishonored, but removed. No other I know of, maybe Splinter Cell.
  • Level 13: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols in the future, and more enemies to deal with in a short period of time. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards that spot you will call in for help, leading to increased patrols. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards.
Featured in: Metal Gear Solid (“Whose footprints are these?”), the Dark Mod (guards can notice certain stolen items, and remember if doors were open/closed from the last time checked), Thief (2014) (same as dark mod).
  • Level 14: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards.
Featured in: MGS series from 2 onwards, Thief, Monaco, Not the Elder Scrolls games or Mark of the Ninja.
  • Level 15: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. Alerting enemies will change the concentration of enemies in the larger area of the level from being more distributed to being more focused on the location where alert occurred. Guards across the level will be more investigative and easier to provoke. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards.
Featured in: Monaco, no others I’m aware of.
  • Level 16: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards.
Featured in: It’s a subtle distinction, some form of this is in most stealth games, like a gunshot instantly alerting, where footsteps are just investigation.
  • Level 17: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. I enjoy a cold shower on occasion. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight.
Featured in: No game I am aware of. Edit: Assassin’s Creed

2013-10-27_00021

  • Level 18: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight.
Featured in: The Dark Mod and nothing else.
  • Level 19: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Entering an area where guards cannot follow will trigger them to flush that area out, such as by using ranged attacks against players that are high up and grenades or gas against players in vents. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight.
Featured in: Deus Ex Human Revolution (grenades in vents), Mark of the Ninja (looking into vents and shooting into them), Dishonored/Thief (2014) (throwing rocks or shooting at characters unreachable with melee).
  • Level 20: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. Entering an area where guards cannot follow will trigger them to flush that area out, such as by using ranged attacks against players that are high up and grenades or gas against players in vents. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards can notice broken passive security measures and reset them to their initial state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight.
Featured in: The Dark Mod/Thief fan missions (relighting torches), Monaco.
  • Level 21: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. When investigating, guards will occasionally detect the position of the player directly when their senses cannot otherwise detect the player, leading them to investigate in the player’s general direction. Entering an area where guards cannot follow will trigger them to flush that area out, such as by using ranged attacks against players that are high up and grenades or gas against players in vents. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Clowns appear in the player’s dreams while they sleep. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards can notice broken passive security measures and reset them to their initial state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of missing guards. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight.
Featured in: Thief 1 and 2 (it’s cheating, but it does help keep the enemies on the player’s tail and makes evading them as you get back into their unaware state more interesting, especially if tuned well).

2013-06-12_00006

  • Level 22: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. When investigating, guards will occasionally detect the position of the player directly when their senses cannot otherwise detect the player, leading them to investigate in the player’s general direction. Entering an area where guards cannot follow will trigger them to flush that area out, such as by using ranged attacks against players that are high up and grenades or gas against players in vents. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards can notice broken passive security measures and reset them to their initial state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of guards identified as missing from their patrol. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight. The player can disguise themselves as an enemy, avoiding hostility except when performing suspicious actions.
Featured in: Hitman, Monaco, Metal Gear Solid 2 & 3
  • Level 23: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. When investigating, guards will occasionally detect the position of the player directly when their senses cannot otherwise detect the player, leading them to investigate in the player’s general direction. Entering an area where guards cannot follow will trigger them to flush that area out, such as by using ranged attacks against players that are high up and grenades or gas against players in vents. Occasionally frogs appear in your soup. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards can notice broken passive security measures and reset them to their initial state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of guards identified as missing from their patrol. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight. The player can disguise themselves as an enemy, avoiding hostility except when performing suspicious actions. Different disguises are allowed different ranges of action without provoking hostility, in addition to being functional in different areas of the level.
Featured in: Only Hitman has a full implementation
  • Level 24: Guards move around in fixed patrols that occasionally change up. They see you based on your distance from them and lighting, spotting you faster up close in bright light, and upon spotting you they attack you until you are dead, they disengage, or they are disabled. If one of them spots you then the alert is localized to that particular guard until that information is passed along to others. Incapacitating that guard will prevent the spread of alert status among other guards. If you enter an area where they cannot see you, they will stop pursuing directly and begin following a projected path of where you might have moved to based on your last location, until a timer runs out, then they enter investigation phase around your last known location, then another timer runs out and they return to changed patrols. When investigating, guards will occasionally detect the position of the player directly when their senses cannot otherwise detect the player, leading them to investigate in the player’s general direction. Guards aware of the player will take a formation to avoid the player sneaking up on them. Entering an area where guards cannot follow will trigger them to flush that area out, such as by using ranged attacks against players that are high up and grenades or gas against players in vents. Certain triggers like partial sightings, sound, bodies, or other things will trigger an investigation phase where they will look around the source of the disturbance. Guards will react to louder sounds more quickly, and have a larger delay in reacting to smaller stimulus. Actions such as takedowns or other near silent things can now generate noise without making them impossible to use near multiple guards. Guards can recognize signs of the player’s passing (such as footsteps on some terrain or misplaced items) and track them to the player. Guards have a persistent memory of the state an object was in when it was last examined, and will react to that object being in an altered state. Guards can notice broken passive security measures and reset them to their initial state. Guards that spot you will call in for help, leading to increased patrols in the future, and more enemies to deal with in a short period of time. Guards can be killed or knocked unconscious, both attract guard attention, killed guards trigger an alert phase, unconscious guards wake up eventually or can be woken up by other guards and trigger an investigation phase. Guards dynamically create patrol routes in response to missing guards or changes in the environment. Guards investigate around for the bodies of guards identified as missing from their patrol. When in alert mode, guards will coordinate to trap the player by blocking off avenues of escape based on a projection of the player’s route. Guards can be mislead by doubling back or changing route when out of sight. The player can disguise themselves as an enemy, avoiding hostility except when performing suspicious actions. Different disguises are allowed different ranges of action without provoking hostility, in addition to being functional in different areas of the level.
Featured in: Only the Batman Arkham games

Each of these elements in order are:

  1. Spotting you and attacking
  2. Moving around in patrols
  3. losing you when you break line of vision with them
  4. following you after losing sight of you with an imperfect knowledge of your location
  5. stimulus demanding their attention
  6. investigating around stimulus
  7. spotting you based on lighting conditions and distance
  8. changing patrols in response to events
  9. calling in additional guards
  10. the ability to kill or knock guards unconscious, leaving bodies behind.
  11. moving guard bodies once incapacitated
  12. dynamic patrol route creation
  13. environmental player tracking
  14. local versus universal awareness of the player on the part of the AI
  15. Global guard coordination across a level, permanent alert status.
  16. scaled reaction times relative to the loudness of a sound or other stimulus.
  17. trapping the player through multi-guard coordination
  18. Memory of environment
  19. Flushing out safe spots
  20. Resetting security
  21. Psychic searches
  22. The ability to use disguises
  23. Disguises based on level of access
  24. Covering other guards’ backs

No game currently has all the items on this list, and some of the items listed don’t exist in any game I know of. Is there any feature on here that you think I’m missing? Are all of these items actually represented in one game or another? Please leave it below in the comments. If it’s distinct from the elements presented, then I’ll add it in.

Chris Wagar is a regular contributor to Gather Your Party, you can follow him on twitter @aGrimVale.
Advertisements

7 thoughts on “Taking Apart Stealth

  1. Gilgamesh310 November 8, 2016 / 12:13 pm

    As someone else pointed out, Tenchu deserved some love. Although its mechanics are fairly basic by today’s standards, it was the first 3D stealth game, and I thought it was better than MGS1.

    I’m not sure what you think of the radar system in MGS1 and 2. It’s a pretty big contrivance. Do you not take any issue with it. I also feel, games that have quick saves, render most of what you described here fairly redundant. When I played Thief, I mostly just hit quick load, every time I was spotted. With MGS and MotN, you can’t do this at least.

    Like

    • Mulgar H November 8, 2016 / 1:47 pm

      The radar is mostly redundant, to the point that I got used to not having it while playing MGS1 on Hard. The biggest asset it has is letting you know if an enemy from way offscreen is looking in your direction (e.g. you can see a tiny bit of blue on the radar, but not the guard itself).

      I’d say MGS3 Snake Eater (Not Subsistence, the original) had a good solution to MGS2’s problem of enemies offscreen seeing you, by letting you move the top-down camera around to see a bit further.
      It’s funny though how that camera does not work at all with MGS3’s guards because of how massive the levels are in comparison to MGS2 and how far away they can see you.

      In an ideal world I’d love a version of MGS2 that had Snake Eater’s original camera, then the radar would be completely unnecessary.

      Like

      • Gilgamesh310 November 8, 2016 / 2:18 pm

        I spent most of the time looking at the radar. It’s hard not to. Your eyes just get naturally drawn towards it. it minimises going into first person mode a lot too, which is tedious. It would be ideal if MGS2 had Snake Eater’s original camera. I actually like most of the gameplay in MGS2 more than that in 3 as it is.

        Like

  2. Mulgar H November 8, 2016 / 7:03 pm

    Yeah the radar draws too much attention, probably because there’s so much movement in it and it’s brightly coloured.
    It’s strange because the guards already point their gun torches in the direction they’re facing so it seems like the team tried to take into account players who turn off the radar

    Like

    • Chris Wagar November 8, 2016 / 9:59 pm

      The radar exists so you can clearly see the vision cones of the guards. It’s a form of information feedback, same as how majora’s mask did it in the deku palace, so it’s more clear when you’re detected. It’s redundant, but redundancies are helpful for player understanding.

      Like

  3. Gilgamesh310 November 8, 2016 / 11:51 pm

    I never actually said it’s redundant. I was referring to something else when I used that word. I said it was a contrivance that takes your eyes away from the field of play all too regularly. I understand it’s purpose. I just feel the feedback could be handled in a better way. Tenchu handled it better, by having a number gauge, tell you how far away the enemies were.

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s