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This article was originally posted over at Game Dev Daily. Tension, stress, and suspense: these are the bread and butter of a scary game. The best horror games slowly tighten the coil of tension and then release it in short, incomplete bursts. In some ways it is the apex of engagement: the player is so enthralled with the experience that it causes him physical stress. Good horror games have an agenda, and it goes beyond cheap haunted house titillation. Horror design is about maximizing player engagement and creating a deep emotional investment. Make no mistake: the best horror games use the engaging nature of scary content to speak to their players intimately. Horror games can address topics that other genres might not be able to support. The purpose of scaring the player is to allow them to be receptive to all the other things you want to say. Of course, most of the scares in games are not the direct result of game design but rather of storytelling. Setting, atmosphere, and characters are fundamental to hooking the player and raising the hairs on their neck. But games have other tools at their disposal: player interaction and game mechanics. The problem of scaring the player in a video game is not contained to narrative. It extends to every aspect of the game design. This is why creation of tension in video games is a fascinating problem for game designers. This article is about the mechanics of scary video games. It is not about plot or narrative, but rather the design of game systems intended to give your story punch. You can read this as a summary of the patterns we experimented with when developing our mystery/horror game Dead Secret, which shipped for Gear VR in October and arrives on Steam and Playstation soon. This isn’t intended to be a proscriptive document about horror design but rather short list of ideas for using game mechanics to build tension.

Pay Attention! The intent of the patterns below is to make the player so focused on the video game in front of him that he forgets about the outside world. Thomas Grip (Amnesia: The Dark Descent, SOMA) calls this the “sense of presence,” the feeling of actually being in the game world. These patterns are also designed to keep the player slightly off-balance. Game mechanics are often about recognizing patterns through iteration. Iteration is a form of routine, and routines are comforting. To scare our player we need him to believe that he’s not in control, that the rules may change on him at any time, and that his read of the game is fundamentally incomplete. Horror games must maintain a delicate balance between creating this vulnerable, impotent feeling without coming off as random and frustrating.

Thinking in Context As a horror game designer your most important task is to focus the player on narrative context rather than underlying game systems. We want the player to be thinking as if he is his avatar rather than a third party solving a puzzle. Many of the ideas listed here try to move the player’s mode of thinking away from “systemic” problem solving (thinking about stats, min/maxing, design patterns, or even tactical strategy) to “contextual” problem solving (“who sent this note?” or “how do I get out of here?”). Some of these patterns are “bad design” in other genres because they prevent the player from attempting to “solve” the game like a Rubix Cube. But these rules have purpose: solving a Rubix Cube is a lot less scary than, say, trying to determine which Ancient Relics are most likely to serve as a weapon against He Who Has Many Names.

Meaningful Failure One way to align the player to the game context is to make failure meaningful to both the player and his avatar. Reaching Game Over usually means death for the protagonist, but how can we make a virtual avatar’s death relevant to the player? A common approach is just to space save points out so that the player loses progress if they die. This is effective, especially when the save points themselves are interesting (see Alien: Isolation’s slow save point system), but the general concept of save points has fallen out of vogue. Dark Souls is a more modern version of this tension-as-progress-cost system. Another method is to make the actual failing stressful. Indie horror games Five Nights at Freddy’s and Slender do this by combining failure with an in-your-face pop-out scare (see below). We chose this method in Dead Secret to allow for save-anywhere behavior. This model uses the threat of a startling event to stress the player out about surviving.

Rule Obfuscation Hiding the numbers that run the game simulation forces the player to think in context rather than systemically. How much health do I have left? Can the enemy see me? Is this the right way to go? How many shots will this boss take to bring down? In other genres giving the player easy access to this information is generally considered good UI. For horror games, it’s better to only reveal data through some contextual abstraction. For example, Resident Evil and Silent Hill have traditionally used rough categories to display health (“Fine,” “Caution,” “Danger”), even though under the hood they track hit points like every other game. Resident Evil also uses character animation to communicate health. You might not be able to tell how close you are to death, but when the protagonist bends forward and holds their stomach you know it’s pretty bad. Hiding information and rules prevents the player from charting a safe route through the game via min/maxing. It also removes certainty from any given system. When the player can’t be sure exactly how an underlying system works he must rely on the environment and story to inform his decisions. In Dead Secret I tried to do this by removing the concept of a “safe room.” There is no space where the player can be sure that they are out of harm’s way. The antagonist, a hooded killer in a Noh mask, can show up anywhere, at any time. At least, that’s what I’d like the player to believe.

Heart Rate Elevation There is some pretty solid research that suggests that people are more likely to feel scared if they are in a state of physical arousal. The mechanism involved is a brain hack called “misattribution of arousal.” It requires an elevated physiological state, which means the player’s heart rate is up, adrenaline is pumping, and he’s starting to sweat. When paired with scary content coming out of the TV, a player in this state may be susceptible to a “false” emotion. There’s a chance that his brain will mistake the physical response for fear and actually cause him to become afraid. Misattribution is a powerful form of emotional control. But it has a critical requirement: it only works when the subject is not cognizant their own state of arousal. Psychologists showed this in tests by giving shots of adrenaline to subjects. Synthesizing false emotions was only possible when the subject didn’t know what they’d been dosed with. To use misattribution in a game you must get your player excited without him realizing it. The Schachter-Singer Two-Factor model describes emotion as the product of autonomic arousal and a contextual label. Misattribution can occur when brain uses some readily available context as justification for physical arousal. A common way to subtly elevate the player’s physiological state is with difficult, unpredictable game systems. Condemned, for example, uses a visceral, high-stakes combat model. Any lowly enemy might defeat the player if he lets his guard down. Resident Evil’s resource rationing and awkward controls make every encounter dramatic. Siren disempowers the player to such a degree that combat always a risky move. Difficult physical activities, such as hard-core button mashing, seem applicable as well. This train of thought ends in some pretty off-the-wall ideas. Night of Sacrifice, a ho-hum haunted house game, manages to be scarier than it should be because it forces you to walk in place on the Wii Balance Board, which raises your heart rate. Next time you find yourself playing a hard game, take a break and check your palms for sweat. Have you been gripping the controller a little too hard? Is your heart racing? If so, you might be in a state in which the content on the screen is more affecting that it would otherwise be.

Character Design The player must feel scared for his avatar, and therefore you need a character that is easy to put in danger. The design of your protagonist affects other gameplay systems, particularly combat and enemy design. To make a powerful character feel threatened you’ll need an enemy that is even more capable and overpowering. Making a horror game about a hot-shit mercenary who can jump out of second story windows and throw grenades through holes he’s just blown in doors? Fine, but you’ll need to come up with a threat so large and scary that even your ninja gunman is overwhelmed. You might need to kick him down a few notches or take away his guns just to keep your enemy design reasonable. Resident Evil’s penchant for elite police officers correlates directly to the series’ love of giant tentacle monsters. Conversely, a disempowered or “normal” character is much easier to threaten. Silent Hill goes for average men and women because these characters seem less likely to survive the ordeal they find themselves in. The series prefers bludgeons to guns, as wielding these weapons does not give the characters too much power. Amnesia: The Dark Descent casts the player as an archaeologist with an oil lamp — hardly the sort we’d expect to overcome ultimate evil. Fatal Frame and Clock Tower use school girls alone in scary places almost exclusively. Siren’s cast features teachers, students, and other unextraordinary people. The combat and enemy design of these games feed back into the player’s in-game identity. Many of these titles don’t even provide a way to fight back. In Dead Secret, it was important that Patricia, the protagonist, be a self-sufficient and highly effective individual. To disempower her without curbing her attitude, intelligence, or gung-ho nature, we put her arm in a sling.

Pop-Out Scares A pop-out scare is an sudden event intended to startle the viewer. Many players hate pop-out scares because they are hard to avoid. They can give you a jolt even if you know that they are coming. Pop-outs are effective but short-lived, and they tire the viewer out. Many players consider pop-out scares to be cheap mechanisms, the mark of a game without the legs to produce a more nuanced variety of fear. I think that pop-out scares have great utility when used properly. The purpose of the pop-out scare is to wind the tension crank. It’s a primer for slow-burning atmospheric fear that takes a while to get going. The pop-out scare sends the message that the player had better sit up straight and pay attention. This focus makes them much more susceptible to a nuanced assault thereafter. The point of a pop-out scare is not to actually scare the player but to make him worry about the next pop-out scare. Ideally, there should never be a next one. Too many pop-out scares and the tension you’ve worked so hard to coil is prematurely released. Too few and the player might lose interest before you really get your hooks in them. One or two startling events early in the game are enough to put the player on their toes for the rest of their play through. The quintessential example of this pattern is Resident Evil’s first zombie dog attack. The dogs come jumping through the windows after a few minutes of play, startling the player. This moment works beautifully in Resident Evil because it teaches the player that they cannot trust the world to be static. It suggests that enemies could come crashing down on them at any point. This scare is even better in the Resident Evil Remake. By the time that game shipped everybody knew about the zombie dog sequence and was expecting it. But in the remake, the dogs don’t appear. You expect them to, and a bit of glass cracks off the window as you pass, but there are no zombie dogs. This takes the pop-out scare and twists it in a way that keeps it fresh and effective. The new message it sends is “we’ve changed things, and you’re not going to know how until it’s too late.” It’s a smart way to keep the player on their toes, which was the point in the first place. I’m not going to tell you what we do in Dead Secret because that would spoil things.

Negative Space Leave space in your narrative, level design, and game mechanics to allow for player imagination. Provide the player with clues and hints, but resist the urge to explain everything. Not only is this a good narrative tactic, it also serves to focus the player on contextual modes of thought. If the player is busy parsing clues about who had a motive to kill Professor Plumb in the conservatory with the candlestick, hopefully they won’t be thinking about decomposing your game into a truth table. Negative space also creates motivation for replays, alternative endings, esoteric achievements, and all sorts of other retention systems. Do not underestimate the player’s wish to consume every last bit of the story, but never, ever show your hand.

Perception Hacks Once the player is thinking contextually about your game, one way to further increase tension is with perception hacks. A perception hack is a one-off or short-term modification of the game rules that is subtle enough that the player can’t be sure it is happening. When executed properly, perception hacks are deeply unsettling because they suggest that even the basic interface between the game and the player is unreliable and untrustworthy. The poster child for perception hacks is Eternal Darkness, which features fourth-wall-breaking insanity effects. The effects vary and are quite effective (at least the first time). But many games use subtler versions of the same idea. In Echo Night: Beyond, there is a room in which the character walks more slowly than normal. It’s a subtle trick, and it makes the room feel oppressive. Silent Hill 4’s third-person camera starts to twist about its forward vector as the player approaches a door, making the entrance feel foreboding. Condemned moves objects when you look away from them, and Fatal Frame 4 occasionally co-ops the standard item collection animation with a pop-out event. Perception hacks are most effective when used infrequently. As with pop-out scares, they force the player to remain alert and focused. It’s also important to allow these sorts of subtle events to be missed. They must feel organic and natural, as if they could happen at any point in the game. Though this means that some players may miss your clever scare event, those that encounter it will have a much more convincing experience. In Dead Secret we used perception hacks to make mirrors seem untrustworthy. Then we made sure that there are mirrors all over the house in which the game takes place.

Sound Design It’s difficult to overstate the value of sound design in horror games. Many of the patterns above can be executed with sound alone, and a skilled sound designer can make even the blandest space feel ominous. The ins and outs of horror sound design are beyond the scope of this article, but it’s worth thinking of sound (and music) as your primary method for emotional messaging. You set the tone for your game and suggest an emotional response with sound. In this respect sound design is more important to horror games than art and graphics. In Dead Secret we designed each room to have a distinctive sound. We created unique ambient sounds, reverb settings, footfall effects, not to mention environmental sounds for each individual space. My goal was to give every room a subtle theme, an aural watermark that the player would recognize when revisiting rooms. Depending on the room, we also use music and abstract tones to ratchet tension up and down. We found that boomy stingers with a lot of bass worked better than stingers with lots of treble, and that abrasive sounds can increase tension dramatically. Finally, we spatialized our audio using Oculus’ free 3D Audio SDK.