Elephants, on the other hand, NEVER forget

Design by Numbers: Cooldowns

Maximum Cooldown Time: 6-12 seconds

Purple hippos. Green puppies. Red monkeys. Short term memory is an interesting thing. Yellow birds. Blue horses. It can only hold around seven items (give or take a few, depending on your level of concentration.) Which means for some of you “Orange lizards” is going to drive the first animal right out of your working memory. This is why most game controllers have around seven buttons — White spiders, Pink fish — and most successful action games don’t even use that many. Player’s simply can’t hold all those options in their heads at the same time.

Elephants, on the other hand, NEVER forget

Orange elephants.

But the most important aspect of short term memory isn’t how many options player’s can remember, but how long it takes for them to fade. Or how short. Neurological research indicates that we start to forget details as few as 6 seconds after being introduced to them. After 300 seconds we are only half as likely to remember a concept, and after 10 long minutes… forget about it. (Sorry.) So that means, depending on your reading speed, you’ve almost certainly forgot the first animal by now.

This has a direct application in determining the length of cooldowns for abilities in action games. (In this context, a “cooldown” is the amount of time that must elapse after an ability is used before it can be used again.) The player stores the fact that an ability was used in their short term memory, and if the cooldown doesn’t expire before they forget about it, they may never use it again! It sounds preposterous, but how many times have you seen someone go through a tutorial on how to use an ability, use it successfully once or twice and appear to understand how it works, and then get utterly baffled when required to use it again just a few minutes later? How many times has that happened to you when playing an unfamiliar game? I know it has happened to me more times than I can remember. (Sorry again.)

So, if a cooldown prevents a player from using an ability for more than 6 seconds, there is a risk that they will stop using it entirely. An onscreen indicator that a cooldown has expired helps, but habituation and change blindness limit how effective an indicator can be, especially when it changes very rarely. Repetition helps, because it transfers knowledge of the ability into more permanent memory, but even this is tricky because with a long cooldown what the player will be committing to memory is the fact that the ability is unavailable, making them even less likely to use it. The options, then, are to use very short cooldowns — between 6 and 12 seconds — or rely on a very noticeable reminder when ability is available again.

You missed a spot.

Indicators have their own problems

For an action game, where onscreen indicators are not desirable, long cooldowns lead to mechanics that are often ignored and quickly forgotten. Maroon walrus.

Simon says "Come up with a better idea"

Making Enemies III

The final fundamental question that needs to be answered when designing enemies for an action game is:

3.  How will the enemy overreact and expose their fatal weakness?

Every enemy needs a flaw, a chink in their armor that can be exploited by the player. A massive enemy with an equally massive health bar that virtually ignores you as you whittle away isn’t very satisfying. Their defeat is too gradual; the moment of their defeat nearly imperceptible. The true glory of victory isn’t the explosion or the death rattle, it’s before that, when the outcome is guaranteed, but not yet realized. That requires a fatal flaw.

  • A melee charge that travels a bit too far, letting the player get behind them
  • Running out of ammo at just the wrong time, leaving them defenseless at a crucial moment
  • Losing their temper and leaving cover, giving up their advantageous position
  • Realizing a second too late they are standing next to an explosive barrel

The issue for game designers is not the flaw, but calling the player’s attention to it. Shooting at the glowy bits is a common trope. It works precisely because it is a cliche, but it’s about as elegant as putting up a sign that says “Shoot here, dummy.” And not as effective, either. Using Water spells on Fire enemies makes more sense, but is about as exciting as turning a key in a lock. It’s easy to see why so many games have resorted to flashing random button sequences as a facsimile of exploiting a weakness, at least screen-filling UI prompts are hard to miss.

Simon says "Come up with a better idea"

The ultimate warrior

The problem is that there shouldn’t be a problem. Nature’s molded us into natural born killers.  We know when an enemy is vulnerable — from injury or inattention or separation from the herd — we can spot the target of opportunity if we see it. But there is so much going on in an action game, so much happening at such a relentless pace, it can be hard to filter out what is important. That’s why the best flaws are revealed when an enemy reacts to the player, or more accurately when they overreact.

The moment of reaction is ideal because the player is paying attention. Their action caused the reaction.  Everyone over-emphasizes the results of their own activity and focuses on the effects that they cause. They want to watch the ripples from the stones they are throwing. So they will be watching closely and are more likely to notice their opportunity. Also, since the player is the cause of the reaction, they will naturally experiment with it and understand the connection much faster. We are natural scientists, even children employ the scientific method, so giving the player control over the weakness will make them more likely to discover it.

Making it an overreaction will make it more obvious. It can be exaggerated and call attention to itself by being slightly inappropriate. It will also give the player the satisfaction of having outsmarted an enemy. It’s one thing to exploit a weakness they cannot control, but it’s so much better to capitalize on a mistake they shouldn’t have made. Provoking an enemy into a fatal error is one of the most satisfying experiences a game can provide, and the more cunning an enemy seems, the more delightful it is to fool them.

My technique is no technique

Making Enemies II

The second fundamental question crucial to designing enemies for an action game is:

2.  How will this enemy counter the player’s first-tier tactics?

Action games give the player a hammer.  It looks like a broadsword or an assault rifle, but it’s still a hammer.  And when you have a hammer, every enemy looks like a nail.  A nail doesn’t have to do anything complicated to look smart; all it has to do is avoid getting hammered right away!  If an enemy forces the player to reach into their toolbox for a second option, they’ll show that they are clever, and the player will feel clever, too.

My technique is no technique

Good AI

The obvious way to counter the player’s basic tactics is through simple invulnerability.  “That armor is too strong for blasters.”  It’s crucial that this invulnerability is communicated clearly, through the look of the enemy, how they respond to the player’s attack, and any supporting effects or dialog.  If the player doesn’t realize they are not being effective — or is misled into thinking they have done damage when they haven’t — the enemy will just seem poorly tuned.

  • Carries a shield that blocks bullets, but any other kind of attack causes them to drop their shield and expose themselves to fire
  • Cannot be killed with melee attacks and must be thrown into an environmental hazard
  • Bullets bounce off the vehicle, but you can snipe the driver out

A more subtle way to foil the player’s main method of attacking is to preemptively take action to prevent it or require another action be taken before the attack to make it a two-step process.  These enemies appear intelligent, but they still allow the player to user their (hopefully) satisfying primary attack.

  • Takes cover behind an object, requiring the player to flank or drive them out of cover
  • Wears a full-body energy shield that must be taken down before they can be damaged by normal bullets
  • Blocks every sword swing, but is stunned if their own swing is blocked

It is also possible for an enemy to behave in such a way that it is more difficult for the player to execute on their first-tier attack.  This can be difficult to tune for multiple difficulty levels, but if the counter-strategy only works on the their main attack, then players of any skill level should be able to cope by changing their tactical choices instead of having to execute beyond their skill level.

  • Flees out of melee range faster than the player can pursue, but has no defense against ranged attacks
  • Keeps up a constant barrage of fire, forcing the player to hide, but unable to get away from a grenade thrown from behind cover

Again, the idea is not to make an enemy that is difficult or frustrating, or even especially sophisticated, but that has a clear counter for the player’s primary attack.  This will require the player to stretch, tactically, and figure out their alternatives, but any amount of experimentation should be rewarded by a quick victory.

Making Enemies

There are three fundamental questions at the heart of designing enemies for an action game.  The first is:

1.  How will this enemy force the player to react?

Any enemy can be tuned to be deadly.  In fact, overly lethal enemies are often a symptom of a poorly balanced game; nobody enjoys being flattened by an unstoppable steamroller.  And any enemy can be crippled until it is merely a target in a shooting gallery.  When a designer has run out of ideas for making an enemy fun, the fallback position is usually “bullet sponge”.  The key to designing an enjoyable opponent for the player is finding a way to split the difference — forcing the player to react to an enemy without resorting to killing them.

To achieve this, it is important for the enemies to take the initiative and make the first move.  Players will tend to repeat the same tactics over and over if they continue to work.  By preempting their default strategy the enemy will challenge them to improvise, to think more strategically, or to experiment with new tactics.

  • Disarm the player, or prevent them from using their primary attack
  • Invade the player’s space, requiring them to start a fight before they are ready
  • Use a special non-lethal attack that stuns or knocks the player around, preventing them from fighting back until they can counter it

Another good way to force the player to react beyond taking and dealing damage, especially in shooters, is to force them to move.  By making the player aware of their environment — the connectivity of the space and their physical relationship to their surroundings — a well-designed enemy can greatly increase the strategic depth of combat.

  • Attack from a range that is outside or inside the player’s optimal range
  • Deny the player use of an area (as with a long-fused grenade) forcing them to move to a different area
  • Take cover behind an object, requiring the player to switch positions and flank them
  • Charge to melee range, so the player must retreat or change weapons

Another way the player can be made to react is by changing something significant about the fight so they have to re-prioritize their targets or switch tactics.  This change doesn’t have to be immediately dangerous, it just needs to tilt the battlefield in a new direction.

  • Begin a devastating attack with a long wind-up that can be interrupted
  • Perform an attack that ends in a temporary vulnerability that the player will want to exploit
  • Allow the player’s current target to quickly withdraw or become invulnerable, removing themselves from the fight temporarily

Another tool for causing a reaction that is often overlooked is dialog or dramatic behaviors that don’t serve a combat function, but can still influence the player and cause a reaction.

  • Taunt or mock the player to incite anger
  • Announce an upcoming action (like reloading) to draw the player’s attention
  • Threaten or attack one of the player’s allies, giving them a chance to be a hero

Far from being a secondary concern to be considered after an enemy can already fight well, these non-lethal interactions with the player should be designed first and receive the most attention.  Once the player is engaging an enemy with their mind — and not just their fingers and their weapons — they will be having fun.  At that point it is easy to make them more or less lethal as the balance requires.

Nerf Herders?

Against Statistical Design

Statistical Design

I suggested that a good way of improving one’s design sense is by staring at Rorschach Tests, and here is a practical example of the importance of practicing pattern-avoidance.

To me it looks like a designer's brain in a vice

Stop seeing patterns!

This image is a heatmap showing where people most often die on Assembly, a Halo multiplayer map.  These heatmaps were first used by the Halo design team to analyze maps during testing, but were so interesting looking they became part of the bungie.net statistics pages.  This data is so rich — so detailed and specific — it must be useful to a designer in some way, right?  The problem-loving brain of the game designer latches on to this as The Solution and immediately starts searching for The Problem.  It is tempting, given a powerful tool like statistical analysis, to incorporate it into the design process somehow — especially since design is often stranded in a world of abstraction and uncertainty.  Having concrete numbers is a rare treat.

However, what does this data mean?  Are red areas bad?  Should dark areas be eliminated?  Does a well-designed multiplayer map have a symmetrical shape?  What percentage of a map should be yellow?  Something about high-contrast feels unbalanced, so perhaps the map should be revised so that the gradient from safe to dangerous is more continuous.  And areas where nobody dies seem wasteful, maybe they should be removed.  And obviously the red areas will be frustrating, so they should be made safer by limiting line-of-sight and adding cover.  Pretty soon we have a completely yellow multiplayer map, that we have tricked ourselves into believing is balanced because our data looks pretty.  We have fallen victim to statistical design.

Players Aren’t Statistical

Statistics are powerful tools because they aggregate a large number of unique instances into a manageable form so it can be analyzed.  It would be impossible to watch every death of every player across thousands of games and have any cohesive understanding of how often players were dying in a given area.  Given enough examples, we would develop an emotional feeling of dread or security associated with certain spots, but the brain uses a very unscientific method to determine these attachments.  Exciting experiences are weighted much too heavily, which is why the impartiality of statistics is useful in discovering imbalances.  Using statistics to find problems is fine; designers go wrong when they use statistics to evaluate solutions.

Players don’t engage with the game statistically — they experience it personally.  It doesn’t matter if more players are killed standing in a specific spot than anywhere else on the map, what matters is the unique experience of a player killed in that spot.  If they realize that they shouldn’t have crested the hill with no cover that is right below where the Sniper Rifle spawns, vow not to do that again and move on, there is nothing wrong with the map.  Even if they do it over and over, growing more and more frustrated at their repeated mistake and creating a bright red dot on the heatmap, the map is not unbalanced.  However, if players are forced to expose themselves at a single chokepoint, or get sniped through a hidden line-of-sight in an otherwise safe area, it doesn’t matter if it is a rare experience and there is no red, the map ought to be fixed.  Neither of these situations can be found through statistical analysis, and neither of them are fixed by a solution that merely addresses the probability of being killed in a given area.

Avoiding Statistical Design

Some systems can only be balanced statistically.  If there are three factions in the game, and one faction wins 43% of the time, the factions are not balanced.  If a map is intended to be used for two-flag CTF, but the bases aren’t mirror images of one another, then the two sides had better be perfectly fair.  The necessity of reverting to statistical methods is inherent in the design of the system itself.  The designer will be forced to make changes that do not change the unique player experience — or may even harm it– in order to fix a statistical imbalance.  Worse still, players are skilled at detecting when a system must be balanced statistically, but since they do not have access to hard numbers their personal experience will tell them that it isn’t balanced — even when the data says that it is!

Nerf Herders?

Nerf Paladin?

Well-designed systems do not need to be balanced through data-manipulation.  If there are 10 weapons in the game, and one weapon is responsible for 20% of the kills, there is probably not a problem.  If the unique player experience isn’t negatively impacted, the statistical difference isn’t a balance issue.  So, the easiest way to avoid the trap of statistical design is to avoid systems that must be balanced mathematically in favor of those that can be balanced behaviorally.  If a system requires a large amount of instrumentation and is extremely sensitive to tiny value changes, instead of obsessing over statistical patterns, try revisiting the system’s design and making it less brittle.

He's about to have an experience he won't forget!

Put to the Question

If you want to learn something, read about it.  If you want to understand something, write about it.  If you want to master something, teach it.

– Yogi Bhajan

Successful designers are those that have the discipline to edit their work.  Generating gameplay ideas is exciting and easy; discerning those with potential and removing the rest takes resolve and vision.  But you’ll never get where you are going if you walk down every road — you must cut!

Removing game elements is usually straightforward.  They are almost always part of a collection of similar elements, so they can be compared on an apples-to-apples basis.  They are often specific instances of a general system — the Assault Rifle is an instance of the Weapon system, the Goblin is an instance of the enemy AI systems — which means that most of the work that goes into them can be applied to other elements and isn’t wasted.  An element is associated with a certain amount of work that must be scheduled for the models, textures, effects, sounds and animations, so it is easy to measure its impact on the overall scope.  And finally, since an element is by definition discrete, it can usually be removed with virtually no impact on the rest of the game.

This guy's name is Needler

Some elements just don't fit in

“Is this mechanic going to be fun?” is a good question, but impossible to answer.  Prototyping can help, but it still takes discernment to recognize the potential in a prototype.  It also represents an investment of resources, which can bias the team toward keeping a prototyped mechanic that ought to be cut.  “Can we implement this mechanic?” is also a good question, but “can” is not “should” and “implemented” is not “tuned”.  “Has a mechanic appeared in another game?” is a useful question, but isn’t necessarily relevant to the current game.  “Does everyone agree this mechanic is good?” is a seductive, but destructive, question; it replaces a designer’s instinct with general consensus and will lead to “downhill design” where the only possible solutions are the easiest ones.  The single best question for determining the potential of a mechanic is “Can the player be taught to enjoy this mechanic?”

He's about to have an experience he won't forget!

Not everything is teachable

Answered honestly, this question has far-reaching implications.  If a player never uses a mechanic, it might as well not exist in the first place.  If a player fails to realize that a mechanic exists, it is too subtle or the game is overly complicated.  If a player refuses to learn a mechanic, it probably doesn’t fulfill a fundamental aspiration for them — they will never be interested.  If a player is unable to learn a mechanic, it is probably unintuitive or it clashes with other aspects of the game.  If the designer cannot distill a mechanic down to teach it, they likely don’t understand the mechanic themselves.  If a mechanic can only be learned through explicit tutorial, it probably has an awkward or obscure control scheme.  Any of these problems are fundamental enough to warrant removal.

On the other hand, if a mechanic can be taught effortlessly — or better yet, players discover it on their own — or if mere awareness that an experience is possible is enough to motivate them to learn how to access it, this is a sign that a mechanic is reaching them on a subconscious level.  This kind of mechanic can be integrated into their thought process and lead to a fluid flow experience.

Definition: Role


The features, mechanics, situation and purpose which define an element’s function in a game

According to Aristotle, we can claim to have knowledge of something only when we have understood its causes.  These causes come in four types: the material cause – the matter of which the thing is made, the formal cause – the pattern or idea which that matter takes, the efficient cause – the motivation which formed the matter, and the final cause – the purpose for which it is used.  Once we understand all four causes, we know an object fully.  In game design terms, once we can explain all four causes, we know an element’s role.

The Material Cause

Video games are not physical objects, so technically they don’t require a material cause.  However, they do have underlying components that make their existence in the game possible, like models, textures, effects and sounds.  They also require other engine features like physics, particles, etc.  Some elements even require completely unique features, and explicitly specifying these features is important to defining the role.

The Formal Cause

This aspect of a game element is what we traditionally think of as “design.”  The form of an element is the pattern that it follows and the systems in which it operates – the game mechanics that constrain it.  Aristotle is referring to the Platonic idea of an object, but in-game design this is the Paper Design.  Just as in Plato’s theory, real life cannot match the perfection of the world of ideas; the in-game experience will never realize the paper design exactly, but it does provide an objective standard.  Much like a craftsman making a chair is attempting to create a material version of the ultimate idea of “chairhood”, the designer tunes an experience to get as close as possible to the original game design.

The Efficient Cause

Often called the “moving cause” because it provides the motivating force for an object, the efficient cause is closest to our modern concept of “cause and effect.”  In game design, the efficient cause is always the player and their desires.  A game element that does not have a corresponding player desire will never be used (at least not without coercion) so it is crucial to identify and meet those needs.

The Final Cause

The most important cause, at least to Aristotle, is the purpose for which an object exists.  In a game, this is especially true because games are fundamentally about using tools to solve problems, and game elements are usually classified by the types of problems they solve.  This is why it is so important to limit an element’s power so it is only effective for its designated role; if an element is an effective solution for multiple types of problem it becomes difficult to tell what its purpose is intended to be.  This is also why a problem should be presented before or at the same time as the solution, or else the player will not have a way to categorize the solving element.  This purpose is communicated to the player through affordance and reinforced by rewarding feedback.

Taken together, these four causes define an element’s role.  The features that allow it to exist.  The mechanics that give it a form and constrain its use.  The situation that creates the player’s need for it.  The purpose for which the player will use it.  Once a designer understands all four causes for an element, they understand an element well enough to implement it successfully.

Definition: Verisimilitude


The quality of seeming to be true, of resembling reality

Why is Wii Bowling like a Hemingway novel? (Beside the fact that they are each made better by adding alcohol.) They both benefit from the effects of verisimilitude. Authentic characters and believable dialog enhance the reader’s engagement in a story; they do not call attention to the fact that they are fictitious by violating our expectations about what might really happen. In the same way, the way the player’s movement in Wii Bowling matches the form and timing of real bowling avoids the awkward break with reality many people feel when playing video games.

Verisimilitude is important for many aspects of game design. Poorly tuned physics systems, bone-headed AI behaviors, inaccurate collision tests, unrealistic lighting, and scores of other common problems all result in a game feeling “off” or “fake”. That is why players can complain about an “unrealistic” space marine pulse rifle; even though no such thing actually exists, they have an intuition of what it would be like if it did exist.

Teach me!

Exactly like this...

However, nowhere is a lack of verisimilitude felt more strongly than in poorly designed controls. If an in-game action clashes with the input method to which it is mapped, it will always break the player’s flow and they will never be comfortable with the controls. Ideally, when the player is engaged with a game, the controller fades into the background and they are no longer aware of it, but an awkward or discordant control scheme is a constant reminder that they are playing a game. Here are some guidelines to avoid mismatched mappings:

  • The duration of an input should match the duration of the action. If a single button press is mapped to a melee attack, the animation for the attack needs to be short and responsive, just like the button press. If the animation needs to be longer, it should require several presses, or a press and hold, that takes roughly the same amount of time for the player to execute. Rapidly tapping a button during a grapple is a bit cliché, but it works because it extends the duration of the input to match the onscreen action.
  • Do not map discrete actions to analog inputs. A game where the player initiates a melee attack with the throw on a thumbstick is using an analog input (the range of motion of the thumbstick) to trigger a discrete action (punching a Triad thug in the face) which makes the player feel detached and removed from the action. This is often described as “soft” or “unresponsive”.
  • Do not map unrelated actions to integrated inputs. The D-Pad is not a set of four buttons, no matter how many games treat it as such. It physically represents four cardinal directions, and it is virtually impossible for a player to get comfortable with treating them separately. In the same way, a thumbstick is not a an arbitrary number of discrete buttons arrayed in a circle, and using them that way will prevent most players from engaging completely.
  • Do not use two-step inputs for single-step actions. The easiest way to add inputs to the controller is to use chords, two buttons pressed at the same time. This works great for “zoom” and then “shoot” because it is a two-step action, but is jarring when used for actions that appear to happen all at once.
  • If an action cannot be mapped to the controller, it should be cut. This is the hardest rule, but the most important. Some actions conflict with one another on a fundamental level, and though it may be tempting to cram them both on the controller, the game will suffer for it. It’s better to have a single action that players can execute confidently and competently than multiple actions that are confusing and cluttered.

In Anticipation

Most of the time involved in playing any game is spent waiting.  In a turn based board game each player waits for the others in sequence.  Even in a timed chess game the actual portion of the game spent moving a piece from one square to another is much less than the time spent waiting for your opponent or considering your own move.  A play clock in football allows for 40 seconds of inactivity between plays that often last less than 5.  A  tennis match can stretch for hours, with time eaten up not just between volleys, but as one player waits for the ball to be returned (or not) and then moves into a new position and waits for the fraction of a second it takes the ball to reach him.  Even in an intense bout of Street Fighter, the actual portion of time spent pressing buttons and taking meaningful game actions is suprisingly low.

Take all the time you want

It could be argued, then, that most of what we call gameplay consists of waiting.  Not passive, disinterested idleness, but active, focused anticipation.  One key to understanding why a game is fun lies in analyzing the type of anticipation it creates and how a player experiences that expectant state.

Anticipation of the Unknown

The player has no idea what might happen next.  While every experience begins with this form of anticipation, it is the least desirable.  The power of the mind is its ability to creatively construct predictions, of the future, of the underlying nature of reality, of the internal state of another person, and when it starved of information it becomes inactive.  “Anything can happen” is not a statement of possibility, but of unintelligible chaos, and it is a very uncomfortable place to be.

Anticipation of Result

Heads or Tails?  Rock, Paper or Scissors?  Red or Black?  Who wins, who loses?  This type of anticipation occurs when we have a stake in the outcome, but no control or predictive insight.  We are wired to make sense of the world, and when something resists, it itches.  In the absence of actual patterns, people invent them, which is the basis for superstition and our utter inability to intuitively comprehend randomness.  Engaging curiosity in this way is a useful tool, especially if failure is not punished, but if it never pays off it turns to frustration.

Anticipation of Evidence

We know the hero is going to save the day and get the girl.  Screenwriters understand that their audience wants a comfortable trope and if they violate this tacit desire the focus groups will force a re-write.  But we don’t know how, when everything looks impossibly bleak, the hero will turn the tables.  We are anticipating the moment where the pattern is revealed, the hidden trump card appears, and our faith in the Hollywood formula is proven correct.  This kind of anticipation is present in puzzle games where we know there is a solution, but we aren’t sure what form it will take or how we will discover it.  Nothing is more infuriating than a puzzle we know we are intended to solve, but can’t.

The World before Walkthroughs

Anticipation of Action

This is the primary form of anticipation found in games.  The player knows that soon it will be their moment to act, has a model for making predictions, and is excited to test that model against reality.

  • Queued Action – The simplest form of anticipated action.  The player knows what they intend to do and are merely waiting for the opportunity to execute.  As soon as the game begins, I will move my Queen’s Pawn forward two spaces.
  • Queued Reaction – Preparing to respond to an event, either in the environment or initiated by another player.  Because there is only one prepared action, the response time will be as short as possible.  The instant they stick their head around the corner, I’m going to open fire.
  • Multiple Queued Reactions – Mentally preparing for multiple possible events and focusing on distinguishing between them quickly.  If the ball comes to me, I’ll catch it.  If it goes to the outfield, I’ll be the cut-off.  If it goes toward first base, I’ll cover second.
  • Inductive Prediction – Trying to guess what an opponent will do and act preemptively at the right moment.  (David Sirlin calls this Yomi, or “knowing the mind of the opponent”.)  I bet they are going to try a jumpkick, so I’ll throw my fireball to catch them on the way up.
  • Deductive Prediction – Using knowledge of a player’s available actions to reduce the number of reactions that must be prepared.  He’s carrying the sniper rifle, so I bet he isn’t going to rush my position.
  • Forced Prediction – Performing an action for the sole purpose of forcing another player to make a predictable response, with the intention of capitalizing on it.  In fencing this  is called a second intention and happens when you are driving an opponent to react to your attacks instead of taking the initiative themselves.  I’ll fire at his feet with my rocket launcher, which will force him to jump into the air and leave him unable to dodge my second rocket.

One important aspect of game design is intentionally inserting gaps in the action to allow for the desired anticipation.  A simple game that has too few possibilities or happens too slowly will fail to fill the time between actions and become dull or predictable.  A game that is overly complex or happens too quickly will cut short the player’s anticipation and feel out of control or chaotic.  Giving the player control over the pacing may encourage them to over-think their actions.  A small change in the cadence of a game, or providing more or less predictive information, is often enough to change type of anticipation, which is a powerful tool for adding gameplay variety.  Understanding and tuning anticipation is crucial to crafting a fun experience, because once anticipation is gone, boredom sets in.

Reciprocal Difficulty

Push on the wall.  This is not a metaphorical encouragement to seek innovative solutions.  Literally, place your hands against a wall and give it a shove.  Now, assuming that you are not working in a cubicle, you have just experienced what physicists call a normal force.  The wall pushed back against your hands with the exact same force you used on the it.

Purchase Gotham City Mutual's Superman Insurance!

Unless you have superhuman strength... Sorry Superman

One of the prerequisites of a flow experience (as defined by Mihaly Csikszentmihalyi in his seminal work Flow: The Psychology of Optimal Experience) is that the difficulty of the activity roughly match the ability level of the participant.  If it is too easy, they will not become completely absorbed and lose themselves in the activity.  If it is too hard, they will become frustrated and unable to make continual progress.  Balancing between these two extremes is the responsibility of the game designer, but often there is not a single setting that works for every player.

One solution is to allow each player to choose their own difficulty level before starting the game.  Unfortunately, the vast majority of players simply choose the default option in their haste to start playing.  Very few players will admit to needing to play on Easy difficulty, and even good players may be too intimidated to start out on Hard.

Every answer seems insulting

I'm tough like week-old bread

Another solution is to dynamically change the difficulty of the game based on an ongoing evaluation of the player’s skill.  But in practice, this automated system usually destroys the intended pacing of the game.  A well-designed game will have periods of less challenge that lead to a more difficult section, building and relieving tension through the gameplay.  A dynamic difficulty system that is too sensitive will add wild fluctuations on top of these natural curves, obscuring the overall effect and flattening out the tension.  One that is tuned to adjust more slowly will often react to the easier segments by ratcheting up the difficulty at the same time that the designer is increasing it for pacing reasons, resulting in an unintentionally large difficulty spike.  Not to mention that the player’s sense of accomplishment will be undercut if they realize the game is “letting them win” by compensating for their low skill levels or “cheating” by getting harder as they get better.

A better solution is to learn from the wall’s normal force and design mechanics that match the player’s skill with reciprocal difficulty.  (Calling this technique normal difficulty seemed confusing.)  In a game with reciprocal difficulty, the more aggressive the player is, the harder the game gets.  But when the player becomes overwhelmed and stops pushing, the game immediately gets easier.  This allows players of all skill levels to be challenged; a good player will play more aggressively until the game gets hard enough, and a less skillful player will proceed at a slower pace until the game gets easy enough.

Examples of reciprocal difficulty mechanics:

  • Recharging Health – If a player is too aggressive and tries to fight too many enemies, they will die quickly, but as soon as they withdraw from combat their health recharges and they can proceed more carefully.
  • Defensive AI – Enemies that are much more effective when fighting from a defensive position are naturally more difficult when the player is pushing hard against them, but allows a timid player to pick them off slowly without putting pressure on them by chasing them.
  • Optional Objectives – Puzzle games that can be solved simply by any player, but have optional collectibles or rewards for completing a puzzle in fewer moves provide more challenge for better players.
  • High Scores – Any mechanic that encourages players to play for a faster time or to score more points is better able to satisfy a variety of player skill levels.
  • Character Leveling – If a player is having trouble with a difficult section, they can make it easier by earning experience and making their character more powerful.
  • Press Your Luck – The player is allowed to periodicaly save their progress or reduce their difficulty level, like going back to town in Diablo or repairing their aircraft in Crimson Skies, but good players will take this option less frequently.

Exaggerated Causality

This is one of my favorite screenshots of all time:

...nothing but net

Elaborate by Dewski14

In one frame, this screenshot tells an epic tragedy worthy of Sophocles himself.  Red Sniper, furious at Blue Man for stealing the attentions of his bride, Grenadina, confronts him in an alley behind the cathedral.  After a heated exchange, the jilted lover fires a single shot at his rival, who ducks out of the way, and the hateful bullet ricochets into the heart of his beloved, who was hastening to tell them they were actually brothers, separated at birth.  The story can be told because the causes and effects are so cearly linked; by exaggerating the causal relationships and drawing out their interactions, a confusing or seemingly random event can be transformed into a dramatic moment.

At a basic level, a game can be interactive only because it is a simulation, a systematic collection of cause and effect relationships.  It doesn’t matter if the world being simulated is rigid shapes dropping into a well, a jungle teaming with Jurassic wildlife or a city populated with tiny citizens, it’s the cause and effect nature of a simulation that allows players to make predictions, develop skills and play the game.  Some game simulations have explicit causal relationships.  “If you pass “Go” then collect $200 from the bank.”  Others try to approximate the real world, including the complex cause and effect events, with more or less success.  Unfortunately, the connections between causes and effects that are obvious in the real world are often difficult to track in a game, making them unnecessarily hard to understand and master.

Like finding a barrel in a haystack

The "Where the %@$# Am I Getting Shot From?!" Effect


Linking Cause and Effect

The best way to increase the intelligibility of your simulation is to increase the strength of the link between cause and effect in the player’s mind. 

Don’t Poke the Lizard Brain.  The human brain is not like a computer; it doesn’t have a lot of computational horsepower that can be applied to arbitrary problems.  What it does have are highly specialized neural circuits designed to perform a single task very efficiently.  Just like your graphics card is specifically made to render 3d scenes, there are parts of your brain devoted to almost every function you need to operate in your daily life.  There are circuits for determining the direction a sound is coming from, circuits for reading the emotions behind facial expressions, circuits that use shading to determine the shape of an object, circuits for predicting the path of a falling object, and countless other abilities we rarely notice we have.  The problem is, these circuits are so finely tuned for reality that the slightest deviation in a game simulation disorients them, destroying the player’s suspension of disbelief.

So, if a grenade explosion sounds like it is coming from the wrong place, players won’t understand that the grenade is what killed them.  If a character’s mouth doesn’t move right, instead of conveying the emotion of a scene they enter the uncanny valley.  If the lighting on an object is incorrect, or the physics system doesn’t make it behave accurately, players will not be able to predict how it will move or how they should react.  If players are constantly confused by what is happening and unable to describe the cause and effect relationships in a game, it is often because the simulation is off, even by a small amount, and must be tuned properly.

Create a Visual Connection.  The connection between cause and effect can be reinforced with simple visual elements.  If a blue-green gun fires a blue-green projectile that explodes with a blue-green explosion that leaves a blue-green decal and causes the player’s screen to flash blue-green, they will probably be able to connect the dots.  Another technique is to conserve the momentum of the cause in the effect, so if the player is melee attacked by an enemy charging from the right, throwing their body to the left in the direction of the attack helps link them in the player’s mind.  If a certain spell causes an enemy to become confused, use the same little stars on the spell icon that are circling the confused enemy’s head.  If one character is using mind controlling powers on another, actually draw visible waves of telepathic force between them.  If an ancient artifact slows down anyone standing within 20 feet of it, attach a visible effect that extends 20 feet to indicate the range.

Avoid False Causes.  It is also important to avoid creating false connections in the player’s mind between unrelated events.  Entire lobes of your brain are devoted to finding patterns, and sometimes the unfamiliar experience of playing a game puts them into overdrive and your mind doesn’t just recognize patterns, it invents them.  “I swear, every time I hear the sound of the timpani in the background music, I take damage.  I must find a way destroy the percussion section!”  Often these coincidental connections are difficult to predict, but they can be avoided by removing superfluous sounds, effects or actions that are not related to any game mechanic.  Fires or explosions that are purely for dramatic effect, but can’t actually hurt the player.  Enemy animations that look significant, but are actually just random variations on a walk cycle.  Environmental features that stand out, like switches or doors, but are merely cosmetic.  All of these are prime candidates for false causes.

Temporal Separation.  One of the most effective ways to help players connect a cause to an effect is by slowing it down.  If a grenade causes a vehicle to explode, delay the second explosion by a fraction of a second.  If flipping a switch causes a gate to open, slow it down so the gate takes several seconds to open completely.  If a headshot does more damage to an enemy, exaggerate and elongate their reaction so it is clear that something unusual is happening.  These delays and exaggerations help the player perceive the two events as separate and sequential steps in a process.  When two events are simultaneous, it is difficult to tell which one is the cause and which the effect, or even if they are related at all.   But a repeated sequence of events is easily recognized and understood. 

Oh, that's what happened...

Call of Duty's Kill Cam delays and replays the cause of your death

Add Intermediate Steps.  If I punch my younger brother and all the sudden I can’t sit down without wincing, I am unlikely to connect the two events.  However, if punch my younger brother, and then my Mom yells at me, and then I have to wait for my Dad to come home, and then I have to go get the leather belt from his closet, and then bring it back and “assume the position” I will probably learn the cause and effect connection.  At least after the first few dozen times.  Sometimes, the easiest way to make a connection more noticeable is by adding intermediate steps to the sequence.  Two events happening in the same order might just be random coincidence.  Five events happening the same way every time is probably not.

Exaggerating causal connections not only helps players learn how to play a game, but it increases the dramatic context of their actions.  It will allow them to construct stories instead of just experiencing a series of events.  And it will make the game more appealing to people that are just watching a video on YouTube, drawing in new players.

Definition: Game Mechanics

Game Mechanic

A single constraint on the possible gameplay actions that determine a part of the player’s experience.

According to our working definition of gameplay, the purpose of a game mechanic is to constrain a game’s interactivity so that it guides the player toward a fun experience.  Tuning these contraints is one of the most important game design processes.  However, in order to tune game mechanics, it is necessary to understand what mechanics are and how they combine to form gameplay.

First, let’s look at how a single game mechanic constrains the possible actions a player can take.  Often these constraints are explicit rules like “If the King is put in check and cannot legally escape, the king is checkmated and the game ends in a loss for that player.”   Sometimes they are limits enforced by the simulation; there are some gaps that Mario can only jump while running.  The most important constraints are usually determined by the game’s control scheme.  After all, the player can only perform actions which are mapped to available inputs.

Another common type of constraint is the player’s objective in the game.  For instance, a goal in Pac-Man is to eat all the dots.  This limits the player’s behavior because any interaction that does not involve eating dots is irrelevant to the game.  This mechanic divides all the entire spectrum of possible actions the player can take into two halves, actions that are permited and those that are prohibited.

More DoTs!  More DoTs!

Pac-Man suffers from OCD

Game mechanics guide the player experience by removing some alternatives and emphasizing others, but by itself, a single game mechanic is not a game and cannot lead to a fun experience.  In fact, a single game mechanic by itself is barely even interactive.  With only one constraint, there is only one option.  There is no room for choice or skill or expression.  To demonstrate this point, I built a “game” based on a single dot-eating game mechanic.


(My free Flash host can no longer keep up with demand, please click this link to load the example.)

In order to actually define an experience, game mechanics must be placed in opposition to one another, much like the legs of a tripod.  That way instead of creating a single boundary (and therefore no choices) they create a region of interactivity for the player to operate within.  This is what Will Wright calls a possibility space.  It is the sum of all the potential gameplay experiences, sort of the wave function of game design.
Triangle Man hates Pac-Man, they have a fight, Triangle wins

Or maybe the Triforce of Game Design?

Definition: Affordance

Affordance  (Also:  Usability, Discoverability, Intuitiveness)

The quality of an object or environment that allows a Player to intuitively discern and perform the gameplay action associated with that object or environment.

In his most profound philosophical work Being and Time, Martin Heidegger makes a distinction between two types of attitudes that we can have toward an object.  First, an object can be “present-to-hand”, which means that it exists and we can observe it and theorize about it.  Heidegger claims that this is an uncomfortable mode for us, that it is inferior to the more natural second attitude where an object has an immediate purpose, which he calls being “ready-to-hand”.

Imagine you are walking through a Home Depot and see a collection of hammers hanging from pegboard in the tool section.  Let’s say you are an English major and you have never seen a hammer before.  You might assume that you had stumbled into an unusual art gallery and start admiring the variety of colors and shapes the artist had created.  Clearly they are a phallic representation of our patriarchal history…

In this example, you would be treating the hammers as if they were “present-at-hand”.  In a game, every time the player is forced to stop and think about the possible actions an object affords they are forced out of their flow state.  If this happens too often they will never be able to relax and enjoy the game.

Killer Queeeeeen

Chess - A terrible example of percieved affordance

Now imagine you are in a burning building and the only exit is blocked by a flimsy plywood door.  This time when you see the hammer on the wall you do not perceive it as an object, but as a tool with a clear purpose.  There is no hesitation because there is no analysis.  The hammer is “ready-at-hand” and that door is “ready-to-smash”.  There is no break in flow because both the hammer and the exit door have clearly perceived affordances.

This is especially important in games, because the player cannot even begin to play until they understand what actions they can take.  The faster they can understand what is possible, the earlier they can get past the theorizing state and into the flow state of proper play.