"The Death Spiral". All of you who have played True20, World of Darkness, Shadowrun and many more games where combat is supposed to be "gritty", "tough" or "realistic" are familiar with this phenomenon: the character is hit and as a result his defences drop, making it more likely for him to be hit again, again making his defences drop—and so forth. The character is in free fall towards dying.

What mechanism is at work here? One called "positive feedback". Succeeding in a certain action causes a series of events (either long or short, it doesn't really matter), which eventually cause the chances of another success to increase, or increase the power of the next identical action. Every time the character has successfully achieved something—most commonly, landing a blow on an enemy,—it becomes easier for him to do so the next time. For instance, where before you needed to get a result of 15 and more on a d20 roll to hit, afterwards 12 suffices.

Use in Combat

As has been mentioned, this mechanism is most commonly found in rules about damage and wounding, where, despite its name, it doesn't represent anything "positive". Let's take True20 as an example. When characters are damaged, they enter various states, such as "dazed", "staggered" etc., which lower their defence, making it easier for enemies to hit them in the future, and also give them a penalty to the toughness saving throw, used to determine the severity of future damage taken. (There are various other effects in addition to these two, such as losing actions, which make it difficult for the characters to fight effectively).

Game designers often employ positive feedback in combat in order to make it more lethal, out of belief that it will cause the players to avoid combat. This, however, isn't true, often because the players don't really bother to stop and think about their actions for too long, and also because combat is rarely entirely avoidable. What it does lead to, however, is players using the death spiral to their advantage—by trying to be the first ones to land the blow.

In other words, using positive feedback in combat doesn't cause players not to fight—it just causes them to fight differently. It makes combat shorter and nastier. Seeing that landing the first blow is important, it encourages dirtier and sneakier tactics.

That said, for combat to actually become shorter, proper design is required. When being hit causes a character to lose actions and makes it harder for him to hit the opponent, it works well with only two combatants. With more than that, however, it may often happen that combat doesn't become shorter—rather, everybody defends poorly and attacks poorly and doesn't get to do much each turn. In other words, when being hit in combat affects both one's ability to attack and one's ability to defend, careful design is needed so as not to make combat with multiple combatants a drag.

Creating Despair

Another place where positive feedback is often seen is in mechanics which simulate gradual descent and degradation: sanity loss (the closer you are to the brink of madness, the more fragile whatever left of your sanity is) or addiction (the more you use the substance, the more addicted you become, causing you to use it even more frequently). As an example for this usage, let's consider a game where the characters are half-demons fighting to retain their personality and consciousness. The characters have a trait called "humanity". Every time a character commits an act of cruelty, she must succeed in a humanity check. Failure causes her to lose humanity, making it harder to succeed in the next check, thus representing the gradual decline in the character's humanity.

Positive feedback fits extremely well for these situations, as it creates a distinct feeling of inevitability. However, the line between a thematic feeling of despair and that of frustration can be quite thin—often depending on the players at hand. Additionally, as should be obvious, not all games benefit from mechanics for creating gloom and despair.

Momentum

Positive feedback can also be used in something actually "positive", in order to create momentum: a successful action increases the chances of success for the next action. (This has been partially implemented in Rolemaster.)

Quite often it is a case of a loophole in the system—positive feedback which the game designer hadn't taken into account. Examples in this department are abound—an especially illustrious one would probably be Pun Pun, the low level kobold from D&D 3.5 who could defeat anything that moved.

But it can also be designed on purpose, in order to generate momentum and have the players feel increasingly awesome as a conflict continues to develop in their favour. You might have noticed that giving penalties to the opponent provides more or less the same effect, and it is, technically, true. The difference is in where you put the emphasis. Giving bonuses to the characters doing the action emphasises their awesomeness as the conflict progresses.

The players often enjoy the situation—so long as it works in their favour. When the bad guy begins getting momentum, the players turn a bit sourer. However, from personal experience, this usually creates decisiveness instead of despair (as long as the bad guy can still be reasonably defeated, that is.)

Additional Uses

Positive feedback is also at work in many skill systems, where it is used to balance out the characters' ability to try again what they just did—every time you fail to do something (pick a lock, for instance), it becomes harder to succeed in it the next time you attempt it.

Negative Feedback

Negative feedback is the reversal of the mechanism—the more you succeed in doing something, the harder it becomes to do so again.

This is often used to limit the use of abilities that control other characters or extract information. The first piece if information is easy to gain, but following pieces are progressively harder to attain.

This can be used as a general "balancer" on abilities. Instead of limiting the number of uses for a certain ability, one can instead make consequent uses of the ability progressively harder (and from a certain logical perspective, limiting the uses of the ability can be seen as the logical extreme of the same approach—it becomes so hard that it's immediately impossible.) This is sometimes used with the ability to do magic—casting spells makes the character tired and hurt, thus rendering him less capable of casting spells in the immediate future. This has been implemented in Shadowrun and perhaps most famously in Dragonlance.

Another use of negative feedback is at character creation, where you get diminishing returns from advancing your character along a certain path. The more points you buy in an ability, the more the next point costs; the second skill in a skill tree is less effective than the first, etc. This is implemented in certain point-buy variations in D&D and in Wilderness of Mirrors, for instance. The purpose behind this design is to encourage players to create more diverse characters, instead of focusing on a single avenue of advance.

Obviously, the opposite method can also be applied—if you want characters to focus on a specific path of advancement and not stray, you can have advances cost less and less. This issue will be further discussed when we talk about character advancement.

Limiting the Effect

There are several methods to limit the effect of the positive feedback mechanism. The first and most often used method is to put a cap on what can be gained through it—the penalty from taking damage cannot be more than a certain number, the bar cannot go lower than a given point etc. There are almost no instances of positive feedback without such a cap (unless by mistake), since it gives much better control over what is happening in the system and prevents absurd situations.

Another option, which is also quite popular, is the inclusion of abilities that allow one to disregard the adverse effects of the death spiral. "Pain resistance", for instance, can make the whole mechanism irrelevant for a given character.

A third option, which is available if the mechanism is tied to a certain bar (sanity, hit points etc), is simply to give the players the option to refill it—heal, get psychological treatment, pray and atone and so on, depending on the nature of the bar.

A fourth option is to have the positive feedback turn into negative feedback when it reaches a certain point. The penalties (or bonuses) become smaller and smaller until they finally reach (or converge to) zero. For instance, you get a penalty of -1 on the first wound you get, then on the third, then on the seventh etc. In effect, this is a variation on putting a cap on the mechanism, only making it "less sudden".

The last, and perhaps most interesting, option is to put the "reset" button into the hands of the players: give the players the ability to remove everything that has been accumulated thus far and start anew. Such a method is often tied to the player's ability to gain narrative control in general (which will be discussed in the future.) This approach is used in True20, where the characters can spend Conviction points in order to get another chance to heal damage or to automatically heal damage.

This last option isn't good for every game. It's fitting when the characters are heroes, extraordinary individuals, who are better than ordinary men. Thus, this option is at home in action and pulp games. Such a mechanism would be out of place in a game where the characters aren't expected to be special simply because they're the heroes of the game.

Summary

Here we've discussed the game mechanic of positive feedback, commonly known as the death spiral. The main thing that it does is make things more extreme—when something bad happens, it soon gets worse and become a catastrophe; when something good happens, it soon becomes overwhelmingly awesome.

When you implement this mechanism, you should carefully consider the consequences, since unchecked it can cause the system to break, but when used with caution, it can be very effective in putting the emphasis where it is required.

Example of Usage

Finally we'll demonstrate the various concepts we've discussed by a small design example. Let's consider a game which centres on the characters' despair. We want the characters to become more and more desperate as the game goes on. Thus, we introduce a penalty on the characters' actions, which increases when the characters fail in their task. The more the characters fail, the more desperate they become, and the higher is the chance of failure.

Next, we think that the game should also be about the characters' reasons to go on and continue at their task. We introduce a mechanism which allows the characters to "refill the bar"—every character has something he cares about, something worth fighting for. Every time the character remembers his cause and his raison d'etre—for instance, when meeting somebody else fighting for the same thing, or when vividly experiencing the consequences of not having that which he is fighting for—some of the penalties go away. Thus, the system encourages the characters to continue fighting for that which is important to them.

Finally, we want to add an aspect of personal revelation to the game. A powerful moment in the story where the character realises something very basic and very powerful about himself or the world, and emerges refreshed, his forces restored. In other words—the "reset" button. When the character undergoes a powerful dramatic moment (for instance, when something dear to him is saved from destruction through his actions alone), the character has a "revelation"—all penalties accumulated prior to that moment are erased completely. The player now has reason to look for this sort of drama in the game.