[In this editorial, originally printed in Game Developer magazine's September 2010 issue, editor-in-chief Brandon Sheffield discusses the importance of mystery in games, and how the unknown gives players the urge to see what lies around the corner].

“Nothing is so frightening as what’s behind the closed door. The audience holds its breath along with the protagonist as she/he (more often she) approaches that door.” So writes Stephen King in his non-fiction book on horror, Danse Macabre.

King was not the first to make this point, nor will he be the last—with the right setting, the closed door, with all its possibilities, can be a frightening thing. Contrast that with an open door with light streaming through it, a traditional symbol of hope.

But the closed door nags at you—don’t you want to know what’s on the other side? The real power of the closed door is the mystery behind it. So long as it’s closed, the possibilities remain infinite.

That constant barrage of mystery is incredibly enticing to players, and is often directly responsible for that “just one more ...” feeling that many games aspire to.

This idea has been used in games for years, occasionally in ways that are analogous to the one King discusses, such as the simple build of tension you might see in the Silent Hill series. As the player approaches a locked door, disconcerting noises increase in intensity, and maybe the world begins to erode, as happens in the series.

The player has to go through the door, there’s no other way—but they almost don’t want to. The player is complicit in the act of approaching the door, which by turns increases or decreases the horror, depending on how much the player already knows. In film, the viewer is less likely to have advance knowledge of what lies beyond—but in games, we might have gone through the same scenario a few times, diminishing the effect.

Unrealized Dreams

Unfortunately, the payoff is usually not as exciting as that anticipation of terror. Essentially, the imagination usually cooks up something far more exciting than anything we can deliver as developers.

The concept is similar to the classic “Pavlov’s Dog” experiment, in which researcher Ivan Pavlov rang a bell (or gave some sort of other stimulus) every time a dog was given some food—over time, the dog would start salivating as soon as it heard the bell, regardless of whether it got any food, because it associated the sound with a reward. In games, as long as there are constantly new things to anticipate, the mind can continue to invent new potential rewards.

This is basically the way we condition players with things like treasure chests and monster drops. They know there’s something in there, so they’ll fight through hell and back to get to it, even if (in the case of JRPGs especially, but also in Western stalwarts like Diablo) it could be a trap, or a monster in disguise, or have some other sort of ill effect.

Over the years, we’ve come up with a pretty well-accepted formula for this, used (with some variation) by games from World of Warcraft to Persona to Borderlands. Chests will generally have something good in them—the excitement is in not knowing just how good it’ll be. This keeps players digging for more chests to get that epic loot. The same applies to items grabbed from felled monsters.

Taking it further, this idea of mystery applies to dialog-heavy RPGs like Dragon Age or the Persona series. Whenever the player is given a set of response choices in a dialog scenario, there is an air of mystery—how will the other character respond?

You generally have some sense of it—choices generally yield semi-predictable responses—but again, you don’t know just how it will affect your relationship with this character in the long term. Therein lies the mystery.

This not only helps strengthen the illusion that you’re building a relationship with a character (alongside positive and negative feedback, which both aforementioned games provide), it also keeps players digging to see what will happen. The “just one more” idea returns.

Mystery Versus Luck

This sort of mystery I’m talking about is a subset of luck. It’s far more specific, and as a result is easier to control. It can be frustrating in a game like Puzzle Quest to have your opponent hit you with a huge chain of “random” attacks, or to have your weapon randomly break in an RPG. That sort of luck can be frustrating. With the mystery of a treasure chest that may drop an epic weapon though, the outcome is always positive, which makes for higher engagement and less frustration.

Mystery isn’t always good though—choosing a difficulty level before you’ve started the game, for example, tends to lead to frustration.

Genres other than RPGs seem less able to use the more straightforward tricks. Borderlands is an exception with its randomly generated weapons found in treasure chests, but by and large FPS games have to rely on a set group of weapon drops from downed enemies.

So how do we get this “just one more” phenomenon in other genres? It’s a very “gamey” sort of interaction, which potentially goes against the realism many games strive for, but MMOs and some online FPS use the anticipation of leveling up in a similar way, and fighting and racing games often use unlockable characters or outfits. These are far less of an addictive gameplay element than they are a bonus, but the concept is similar.

In all, I think most games would be well served by including some element of mystery. It adds stickiness, and keeps players playing long after they might otherwise have stopped. It forms a strong link with the player, so that they keep playing “without knowing why.” Games that don’t do this tend to fall by the wayside. Seems an obvious choice to me!

[The September 2010 issue of Game Developer magazine, the sister print publication to Gamasutra and the leading U.S. trade publication for the video game industry, has shipped to print and digital subscribers and is available to potential readers in both physica/digital subscription and single-issue formats.]