Stealth games are a niche game genre that tasks players not with defeating enemies, but avoiding them. Some stealth games focus on breaking line of sight and avoiding enemies, while others make players the master of their domain, carefully picking off enemies, gathering intelligence, and sneaking by.
Stealth games are tricky for designers to get right. Travis Hofstetter, a designer for the Tomb Raider reboot, mentions two main challenges designers face when making them. The first is achieving smooth gameplay. Buggy geometry that enemies are able to see through and missing cover makes players give up on stealth, period. Second, designing stealth often means designing two games. One game is built for the sneaky player, and another for the aggressive player that wants to run through and fight.
Getting the complex systems right is difficult, so read on to learn about the core principles of the genre’s best games. Understand the foundations of level design in a stealth game, and how enemy behavior works together with the level to create a challenging and satisfying experience. There are few resources online for creating a stealth game from scratch, but learn about what is out there to get development started.
What are the principles of stealth game design?
The principles of stealth game design are player choice, robust enemy detection rules, and the sense of a dynamic world that keeps going when the player isn’t looking. Stealth games communicate the game state clearly to the player, then set them loose to complete the objective. The core of stealth is avoiding enemy detection to reach a goal, but a good stealth game gives players multiple choices for accomplishing it.
Stealth games have added significantly to the base player toolset over the years. Stealth mechanics in the genre’s early history have simple detection and movement mechanics. Metal Gear for the MSX2, credited with starting the stealth genre in 1988, shows off these mechanics. Players avoid detection by standing behind cover or out of line of sight. Detected players run away to another room to end combat and try again. The novelty of avoiding rather than engaging battle carries the experience, as it is the earliest and simplest stealth game.
Turning stealth into an empowering experience is a different matter. Thief: The Dark Project overcame the challenge with its systemic design. Rather than avoiding line of sight, the game has a series of rules. Guards investigate sounds, see better in lighter areas, and have set patrol paths. The guards’ systems-based knowledge means players are free to apply real-world logic to the game: “if I throw a rock over here, the guard should follow it!” And the guard does.
The result is a system which gives the players many options but requires many complex systems to work together. A systemic game tends to fully come together only at the end of the development process. The designers had trouble making Thief fun even after a year and a half in development, since getting the AI right and communicating the game state to the player took so much trial and error. Only after a rewrite of the AI and changes to the user interface did the game begin to take advantage of the extensive systems and level design work.
Stealth has become an increasingly marginal mechanic in gaming. Stealth is used as a change of pace in an otherwise action-packed game, as is the case with Uncharted and the new Tomb Raider games. Recent stealth-heavy titles such as Dishonored highly encourage stealth but still make avoiding detection only one tool. Few games, such as Hitman and the newer MGS games, carry the torch of a stealth-focused experience.
Systemic game design is ideal, but the old ways work well in the horror genre for the same reasons it’s fallen out of fashion. Giving players no options but to avoid sight makes the player powerless in the face of the nightmares that lurk in the shadows. Amnesia: The Dark Descent bears only a passing resemblance to the majority of stealth games discussed here. The player has no choice but to run, and they’re player character loses sanity if they even look at the nightmares chasing them.
Detection isn’t as trivial as setting enemies to an alerted state when the player enters their vision. Immediate, unexpected detection from a guard walking around the corner feels random and frustrating. Planning is a core component of a stealth experience. The game needs to communicate the detection system to the player so they’re able to change the plan and respond accordingly. A completely predictable enemy is no challenge, though, and isn’t satisfying to defeat. It’s a balancing act to make sure the enemies are difficult but also fair.
Making detection work correctly means communicating to the player through multiple channels. An enemy’s animations are one channel. A relaxed stance, a cocked ear, a set of searching eyes, or a running guard tell the player how alerted they are to their presence. An indicator above the enemy’s head or on the screen reinforces the feedback in the enemy behaviors. A whistling guard is at ease while running footsteps and shouts tell the player they’re being hunted.
Enemy states range from at ease to fully alerted to give players the chance to get away, keeping the player in control. Enemies first become suspicious, searching for a sound or getting closer to a suspicious sight, then alerted once they are sure they’ve found the player. The player still has time to react at this stage, as snuffing out the one alerted guard before they’ve cried out means the rest of the guards don’t come searching quite yet.
The UI has advanced a great deal since the early days of Thief. There was no model for stealth game UI. One of the great innovations that emerged from playtesting the game was the light gem. Light is so integral to how visible a player is in Thief, but players have a lot of trouble understanding how illuminated they are from first person. A simple icon, the light gem, solved the problem. The gem glows brighter the more illuminated the player is. Since Thief, a detection indicator, an enemy detection indicator, and a part of the UI showing the alert level have been added to the designer toolset for communicating the game state to the player.
Players feel empowered by a variety of options once they know what enemies are doing. Players manipulate enemy AI by making noises or creating other distractions. They alter the environment by shooting out lights or putting down noise-dampening moss. Navigation tools like grappling hooks enable means of escape or reaching areas enemies aren’t able to. The last resort, elimination tools, allow players to take out enemies but carry a greater risk of getting detected.
Challenging the player with all the options at their disposal presents another problem for the designer. Varying the gameplay by giving enemies tools to eliminate certain abilities is an effective way to keep the player on their toes. The player in Batman: Arkham Asylum expects gargoyles to be a safe perch during stealth segments, but later enemies rig them to explode. Enemies in other segments of the game are able to jam detective mode, the player’s x-ray vision, so players must work with an incomplete understanding of the battlefield.
How to design levels in a stealth game?
Design levels in a stealth game by thinking of how to help players. Making an encounter very difficult to sneak through is easy, the challenge of level design is creating scenarios where players are empowered to complete them in a variety of satisfying ways. Hitman and Dishonored are two systemic games which give players an objective and a large environment to achieve it in. The designers set the game systems rolling – guard patrols, enemy AI, tools, and weapons – and the player figures out the rest. Stealth maps build around those rules in two primary ways.
Travis Hofstetter, who designed stealth encounters for Tomb Raider, divides stealth sections into outposts and limited encounters. Each type varies the pacing by changing the amount of time players have to plan, how much information is available to them, and how alerted the enemies are.
The first type is an outpost. Outposts have a safe region outside of the area where players are able to survey the area. The space around the outpost puts the player in greater control, as they not only have a safe area for observation but escape if they are found out. Enemies at the edge of the outpost are sparse, encouraging players to sneak in. The center is dense with enemies, usually surrounding an objective. The player’s also able to escape if the encounter goes south.
The limited encounter takes place in constricted spaces where players must pass certain enemies to get to the objective. The goal of the limited space is to surprise, not defeat, the player. Enemies are visible from at least 8m away before players engage with them. The limited area makes escape much more difficult, and there is more pressure to use the full toolset to evade detection.
The two-fold division, outpost and limited encounter, is most fitting for games that switch between stealth and other mechanics, but the types still apply to stealth-focused games. Metal Gear Solid 3 and The Phantom Pain take place outdoors, in the jungle and desert, giving players opportunities to approach an encounter as they wish. Metal Gear Solid 2 is much more on rails, and many of the encounters in that game hem the player into narrow areas where guards are able to flank the player at any point.
The Hitman games loosely fit the outpost model. The player has safe areas to plan from and escape to in the form of public places. The premise of Hitman is that the player is Agent 47, an experienced assassin and master of disguise. The player poisons, stabs, strangles, shoots, and defenestrates unsuspecting victims in numerous scenarios. The player sometimes infiltrates a home, a club, a racetrack, a spa: no location is off-limits. The challenge is infiltrating the private spaces and implementing an assassination strategy of their choosing.
Hitman succeeds at empowering the player because the level nudges them in the right direction. Players who find gunpowder in the Hitman 2 Sapienza mission later find the cannon it’s usable with. Kitchens and boiling pots of soup encourage players to sprinkle in poison. An area protected by a security guard tells the player to find a guard uniform before sneaking in.
The levels in these games are replayable because the variety doesn’t emerge from scripted circumstances but systems. Disguises in Hitman aren’t a one-mission set piece, but work in all restricted areas throughout the game. The Hitman games are modular enough to support user-created missions, where the player is tasked with killing a different target in a campaign level.
Dishonored is a systemic game that looks at immersive sims for its inspiration. Stealth isn’t the only way to play the game. Players have several magical abilities in addition to a knife and gun that make combat feasible. The player’s objectives, however, aren’t just combat-focused and are achievable through a variety of methods, with each one achievable through combat or stealth.
Dishonored’s level objectives encourage players to explore the game rules and find different ways to complete them. Players in each level have an assassination target, but the player has a lethal and non-lethal way to take them out. The lethal way involves gathering intel and sneaking (or fighting) to the target before taking them out. The non-lethal way varies. In the level “House of Pleasure”, the player must gain access to a safe to secure the non-lethal takedown of the Pendleton brothers. The way to the safe is up to the player. They may save a serving girl and receive her key as a gift, steal the key, or get to the balcony and enter from the unlocked second story.
Future levels react to the player’s actions in Dishonored as well, further making the game feel like it lives beyond the player’s actions. Choosing the lethal option raises the game’s “chaos” level. Doing so increases the number of enemies in each level and sours NPCs’ responses to the player. The layouts of some levels even change. The challenge is in creating the extra content. The more choices the player may make, the more content designers put in that some players are never going to see.
Levels often include vantage points, places from which players are able to survey the level without fear of danger. The open-ended environments and their consistent internal logic give players the ability to think about how they’ll approach a problem before engaging directly with the obstacles. The fun in a stealth game isn’t only in the stealth itself but the ability to plan from the shadows and then execute the plan flawlessly. The Batman: Arkham games make the vertical space Batman’s second home.
Some levels give or restrict information to alter the way players craft a plan. Thief starts your character with a paper map, which sometimes has unfinished details or inaccuracies. Players are left to figure out parts of the layout on their own. Hitman thrives on restricting knowledge in different ways. Players find intelligence, question NPCs, and eavesdrop to learn about targets. Rather than stopping at the pre-level briefing, the intelligence gathering continues into the level in Hitman.
The encounter itself gives players multiple avenues for executing their plan and escaping when it goes wrong. Verticality, ample cover, and branching paths through an encounter are necessary for a successful level. The goal is to get past enemies to an objective, and sneaking past enemies on a flat plane is boring. Overlapping paths and the ability to move up and down to avoid detection is more interesting than crouching behind cover and waiting to advance to another piece of cover.
Consider the types of safe and dangerous areas that make up portions of the level. Placement of light and shadow in Thief is essential to that game’s detection system. Some levels change the formula for world-building and gameplay reasons: the Hammers worship technology and fill their halls with electric lights players aren’t able to snuff out. A game like Hitman has public areas where the player is safe around other NPCs, and unsafe areas are surpassable with disguises. The level environment is allowed a great deal more flexibility when the player’s toolset is so expansive.
Enemy placement varies based on the type of level. Enemies in outpost situations are spread out. A few scattered enemies that the player’s free to take out linger at the edges, with more dense and dangerous situations lurking in the center of the encounter, farther from safety.
Enemies in limited approach levels are at different levels of alert and in various arrangements. Enemies closely guarding an objective must be distracted away or the player needs to find another way in, while patrolling enemies give players avenues for sneaking by or eliminating stray targets. Enemies that are hunting the player box them in and make the player question their safety.
The level must afford players opportunities to isolate enemies. Enemies in bunched groups don’t give the players opportunities to get them alone and take them out. Patrolling patterns ought to be predictable so players are able to plan and choose when they approach. Sparse enemies also allow players to plan one step at a time, taking out the enemies at the edges first, then working inwards to more challenging groups.
The level objective is important to keep in mind. The objective of taking out every enemy reduces the level’s challenge. More interesting are objectives to collect something and evac, as thievery doesn’t require players to engage in combat at all. Thief takes advantage of the objectives to make hard difficulty more dynamic. Rather than increase health or enemy awareness, the objectives add new goals, such as stealing more loot or finding a specific new item. The level opens and closes areas depending on the difficulty as well. Players now must interact with harder parts of the level they skipped on previous playthroughs.
A final type of level, hide or die, is an undesirable approach that doesn’t appear in stealth games often. Players in hide or die levels lose as soon as they are detected. The Tomb Raider reboot uses the trope only once as Lara Croft sneaks past an army. The punishment of death on discovery made the moment more tense. Survival horror often takes this approach, but even games with powerful enemies like Alien: Isolation give players tools for predicting where the alien is, as well as visual cues like saliva dripping from vents.
How to design enemy behavior logic in stealth games?
Design enemy behavior logic in stealth games that signals to the player how to defeat it. Enemy behavior works with level design to ensure enemies perceive their environment in predictable ways. Enemies sense players in two primary ways: through sight and through sound. Once enemies have perceived the player, they must slowly become alerted to the player’s presence. The level of alert is communicated to the player through UI, animations, and dialogue.
Enemy vision cones are more complex than a cone shooting out from the enemy’s face. Martin Walsh of Splinter Cell Blacklist discussed in detail the detection systems in a 2014 GDC. Enemy view cones consist of several pieces of geometry. A forward view cone is a box that represents their best vision. A coffin-shaped box more sensitive to movement serves as an enemy’s peripheral vision. The coffin and box shapes resulted from playtesting. The game started with a cone, but a cone makes vision wider and more effective at a distance, which doesn’t mimic real vision.
Enemies perceive the environment, not just the player. Enemies that react to open doors, bodies left on the ground, or missing items create consequences for every action the players take. Guards become suspicious and start searching, or change their patrol pattern when they notice a door open or another unconscious guard. Guards remarking on what they’re seeing signal to the player the effect they’ve had on the game world.
Awareness of sound also makes enemies feel lifelike and challenging to sneak past. Vision was the only sense enemies had in stealth games before Thief, but the game made hearing an essential ability for stealth opponents to have. Player movements, gunshots, and items getting knocked over are audible and trigger guards to search for the source. The sound system adds challenge, but also utility. The player now has the ability to throw noisemakers and distract guards from their path.
Sounds propagate along navigation paths to guarantee sounds aren’t traveling through walls at full volume. The original Thief had a sound layer of each map that was separate from the navmesh and physical geometry. The designers of Hitman: Absolution discuss a similar approach at the GDC. The studio generated a grid of points based on the navmesh that determine how far enemies are from sound sources.
Enemy alert states keep the gameplay interesting by having enemy patterns react to the player. Enemy alert tends to come in 3 phases: at ease, suspicious, and alerted. When the player escapes a guard who is only suspicious, it is reasonable for the game state to return to how it was before. Alerted enemies who engaged the player in combat wouldn’t reasonably go back to normal. Alerting the soldiers in a town alerts enemies in a whole region for several hours in MGS V: The Phantom Pain. The soldiers walk in tighter formations and take different patrol routes.
Enemy patrols signal to the player how to approach a situation. Patrolling enemies stop at various points in their patrol to give players the opportunity to take them down; there needs to be spaces where the player’s able to sneak past or swoop in for the kill. Enemy dialogue communicates where they’ll go next: if they tell another guard to come with them, the player eavesdrops and knows those two guards will stick together.
What mechanics are used in stealth game design?
The mechanics used in stealth game design are divided between altering player movement, information gathering, AI manipulation, redefining space, and dispatching enemies. A stealth mechanic is a tool that gives the player choices in how to approach an encounter. Players use sight and sound to clock enemies, just as they use the same sense to trick them. Thanks to Mark Brown for his five-fold division of stealth game abilities.
Players are able to alter their movement to sneak past enemies. The simplest tech is crouching, standing, or going prone. Each action changes the player’s visibility, but also how noisy each action is. Walking is quicker but noisy and visible, while crawling is lowest visibility and noise but quite slow. Players sometimes have special abilities like the grappling hook in Batman: Arkham games for quick getaways.
Planning is the first step in a successful stealth encounter, and information gathering is the purpose of much of the stealth toolset. Dishonored players interrogate NPCs, Hitman players eavesdrop on enemies, and Splinter Cell spies use a variety of gadgets for getting information about the area. Leaning around walls, snake cams, night vision, and x-ray vision help players see without being seen in different types of levels.
Players have the ability to manipulate enemy AI to create openings where necessary. Throwing rocks is the typical way to distract enemies, but games like Hitman have more creative options related to their open-ended premise. An overflowing sink or a tossed banana is a suitable tool for redirecting guards. Players in Metal Gear Solid V: The Phantom Pain have a Decoy, which either attracts attention from guards or serves as a way to draw off enemy fire in a gunfight.
Players are able to control what spaces are safe or unsafe, if distracting enemies isn’t possible. Water arrows in Thief let players put out lights, and moss arrows let players lay down a soft, quiet surface. Camo in MGS 3 and disguises in Hitman make players safe in areas that weren’t before.
Even hardcore stealth games such as Thief give players methods for taking out enemies in combat. There is a variety here as well, with melee takedowns, traps, and poisons at the player’s disposal. Silenced pistols in Splinter Cell and abilities in Dishonored encourage players who just want to fight to take a more direct approach. The danger of including combat mechanics is that designers must account for aggressive players. A significant percentage of players always ignore stealth, no matter how good it is, if combat is an option.
Balancing the four types of abilities with each other is crucial. Too much player power means players take out enemies left and right. Fewer living enemies means fewer obstacles for the player to deal with. Limitations to the time an ability is effective or its range make sure the player isn’t in complete control. Echo demonstrates an interesting way to balance the power of player abilities. Enemies in Echo copy all the abilities a player uses during certain periods, from combat abilities to simple ones like opening doors, which makes the player think twice about what they do.
Where to find a stealth game design template?
A stealth game design template isn’t available online, but some resources are available in asset stores. Stealth game designers and immersive sim creators like Warren Spector and Arkane Studios have repeatedly spoken publicly about how they created their games, so look to their presentations for inspiration.
The Unity Asset store isn’t a design template but has a few resources for getting started. The store has stealth game AI packs, which include the typical enemy alert levels. Sound effects for alerted NPCs are available as well, meaning a prototype with working audio is easier to get off the ground.
The Unity templates are relatively few compared to other genres. Stealth is tricky to get right, and all the systems must be vigorously tweaked and rebuilt to work in harmony with each other. An online template is helpful, but isn’t a replacement and won’t have enough to create a complete vertical slice of gameplay. The 2D templates are likely to be the most helpful, as the removal of a dimension greatly simplifies the process for a designer relying on store assets. Mark of the Ninja shows that a 2D approach to stealth is fruitful.
The Dishonored creators have discussed the game’s design principles and development process online at the GDC and in interviews. Their advice isn’t a template but does suggest some best practices in creating stealth games. The Dishonored 2 team recreated the AI system from scratch, and their 1 hour GDC talk features several members of the team describing the specifics of their technical implementation. Steve Lee of Arkane discusses the theory behind his level design approaches in a GDC 2017 talk, where he shares his experience with BioShock Infinite as well as Dishonored.
What is an example of a stealth game design document?
No recent examples of a stealth game design document (GDD) exist, but a general game design template works for stealth games. A translated Metal Gear Solid 2 GDD is available on the internet, but it is more of a game pitch than a GDD. The descriptions of the story and characters are much too detailed. There is no need to look only to the stealth genre, though. The universal components of a GDD are essential for a stealth game: pillars, game premise, and core loop but there are features that are especially important for designing a stealth game.
Our Game Design Skills GDD template comes with a main template and feature docs for creating detailed documentation. The basic indie template starts with sections for core pillars, a gameplay description, and the core gameplay loop. The site has a AAA document as well with more detailed sections for market research. The feature docs that come with it give room to describe the art and code implementation required as well as assigning ownership over different tasks.
Controlling scope is essential for bringing any software to completion. Systemic games have an especially large amount of systems to build and delegate. An AI system tells the enemy how to find locations in 3D space, another layer allows them to perceive sight and sound, combat behavior tells enemies to coordinate in combat situations, and, in the case of Dishonored, killing an enemy changes the chaos level of the world. Each feature mentioned here is composed of code, animations, audio, UI, and visual assets. Keeping feature documents for the parts of these complex systems allows the process to be divided into concrete steps and delegated.
Don’t forget the role of sight and sound in creating feature documents for a stealth game. Each action the enemy does is telegraphed through animations, sound, dialogue, and all the other pieces of artwork just mentioned. Lots of resources from different disciplines are necessary to present everything the player needs to parse the game world.
Stealth games are a niche genre, and there’s so much room to expand on the formula. What other creative responses to the stealth formula have you seen? Are there principles of enemy AI and level design in those games you have to share? Finally, is there anything you would like to add having read this article? We want to hear your feedback, so please leave a comment!
