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.


GDC 2010: Design in Detail XIX

And there it is! The big detail!

It’s a large change. It’s very easy to convince yourself that you can feel tiny changes, but you will be fooling yourself. The balance never hinges on a 2% difference in a single value!

It was a smaller change than we tried initially. I think originally we changed it to 0.9, which broke the flow and wrecked the weapon, but did fix the problem, so we knew we were on the right track. In general, you want to overshoot and then come back. You have to make sure your change accomplishes your goal, and then dial it back.

There are lots of ways to verify that a change was successful. In this case, the Sniper Rifle didn’t get any less popular; People still use it whenever they can get it. But Optimizers stopped using it exclusively.

The other reason we could tell it was balanced was because we could compare how the behavior we were seeing in playtests matched the desired role we described in our paper design. It’s not quite an objective test, but it should help. And most importantly, I no longer got nervous when I watched people use the Sniper Rifle. You should verify a change with both your brains and your guts.

Ship it!

At this point during my GDC talk, the audience started clapping, cluing me into the fact that I was completely out of time.
So I just went with the flow and ended it there, which was fine. I had walked people through the balancing process, brought up the important principles, and applied them to the sniper rifle change. But I had also intended to mention a couple of things about the last stages of balancing, which I will get into next week!

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.

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.

Balance of Power II

Tank Beats Everything

Even in the case where an element cannot be limited by role, it can be limited by availability.  Sometimes the Player should feel overpowered, either as a reward for a good player or as a temporary boost for an average player.  A game that is nothing but a relentless competence test can become monotonous, especially once a player has reached the limits of their physical ability to get better.  Giving them an occassional taste of unmitigated power relieves the pressure to perform and is an excellent palate cleanser.  An element that is fun and fulfills a player aspiration but can’t be limited to a single role is an excellent candidate for this experience.

No mana?  No problem!

Take that, Rock, Paper and Scissors

A successful transition from “balanced” to “overpowered” usually requires some changes, though.  It needs to be exaggerated so the sounds, effects, even the fiction, match the new power level.  It should become a featured element on a single level or two, the player should feel special for getting to use it, and the enemy resistance should be ratched up as well to highlight how strong they have become.  The element should also be made as modal as possible, so the player knows when the “overpowered” experience begins and it is clear when it is supposed to end and resume normal gameplay.

In a Corner

Let’s say an overpowered element doesn’t fit in any of these categories.  It isn’t just a perceived imbalance, the other elements can’t be strengthened to an equivalent power level, the role can’t be limited or enforced, and it isn’t appropriate for an over-the-top set piece.  If nothing else can be done, it has to be weakened somehow, right?  Let me tell you about The Needler

The Needler is a weapon from the Halo series.  It fires a stream of neon pink projectiles that actively track enemy targets.  On impact, each needle embeds itself into armor or flesh, remaining there for a few seconds before detonating and causing further damage.  If a character ever has more than 5-6 needles attached at any given time, they all explode in a particularly lethal chain-reaction known as the “Pink Mist”.  It first appeared in Halo 1 and was the bane of my existence for 10+ years because it was incredibly fun to use, but equally impossible to balance.

Like this, only a couple feet lower

I feel a headache coming on

It would start out too powerful, so we would weaken it.  Which would make it useless, so we would change the mechanics.  Which would make it effective in too many situations, so we would limit its placement.  We ended up drastically weakening it right before we shipped to prevent it from wrecking the game.  Three times!  The amount of effort, thought, debate, programming and art resources, playtesting surveys, data analysis and sleepless nights that were poured into the Needler far outpace any four other weapons combined.

So, even if an element cannot be balanced in any other way, the answer is still not to weaken it, but to cut it completely.  It is too difficult to weaken an element without destroying what made it fun in the first place, and the end results won’t be worth the hassle.  It’s best to just save it for another game where it will fit without compromise.

Balance of Power

“Iron sharpens iron, and one man sharpens another”

-Proverbs 27:17  [ESV]

“The whats-it is too powerful.”  It could be a weapon, an RTS unit, a character in a fighting game, a multiplayer class… it doesn’t matter because all chronic balance problems follow the same general pattern.  The game starts to revolve around a single dominant element, which is inherently overpowered and reduces the game’s strategic complexity, ultimately limiting its longevity.  Nobody notices when a single element is too weak, because they just avoid it.  And nobody complains when a dominant element increases strategic complexity, because that makes the game better and more fun.  And a simple problem, like a damage value that is just set too high, usually has a simple solution that is quickly applied.  But for chronic, fundamental balance problems, the designer is repeatedly faced with the same decision.  Should the dominant element be weakened for the sake of balance?  (Hint:  The correct answer is always “NO!”)

Perception is Reality

First, it is important to recognize that the only “balance” that matters is the balance that players perceive.  The goal of balance is longevity, and if players continue to play because they believe the game is fair, it doesn’t matter if it is objectively balanced in some measurable sense.  In fact, if a large enough community perceives the game to be balanced, but your metrics claim it isn’t, then the metrics are wrong.

Nice Gear

Sometimes power is deceptive

So often the problem isn’t that an element is too powerful, but that it feels too powerful.  Maybe its a gun with a really great firing sound.  Or a new unit that players haven’t figured out how to counter yet.  Or perhaps it appeals more to skilled players or everyone is using it because it is new and novel.  These problems usually fix themselves if they are left alone.  I changed the perception of an “overpowered” weapon during Halo’s development just by announcing that I had fixed it (even though I hadn’t actually changed anything.)

The Tooth Fairy is Overpowered

In almost every case, there is no such thing as an “overpowered” element; there are well-tuned elements in a crowd of underpowered, ill-tuned alternatives.  The Sniper class is implemented and all of the sudden you can’t take three steps without being headshot from across the map.  The problem is not that the Sniper is strong, but that the Medic and the Engineer are weak.  It’s easier to make a potent Sniper, so it immediately outclasses the rest.  Instead of spending time figuring out how to cripple the Sniper, focus on making the other classes equally awesome.  Or better yet, ditch the ones that will never feel as powerful as the Sniper and choose different classes that have their own natural strengths.

Get it?  Because neither one exists!

His only weakness is his terrible agent


Too Powerful, or All-Powerful?

In the paper design balance pass, every element should have been given a role to fill.  Sometimes an element breaks the balance by breaking its designated role.  An anti-vehicle missile that can be used against a crowd of infantry.  A “glass cannon” that can hold his own in a melee fight.  A long-distance weapon that is just as effective at point-blank range.  The solution in this case is not to weaken the element, but to restrict it so that its strength cannot be applied in as many situations.

Often it takes ingenuity to limit a weapon without weakening it, but it isn’t as difficult as it might seem initially.  A global weakness will affect the player in every situation, so a heavy-handed global weakness will be a constant irritation.  But a specific limitation will only be felt when an element is being used outside its role, which a player can learn to avoid, eliminating the annoyance entirely.  Nobody complains that their fancy sports car doesn’t work underwater, they just stay on the bridge.

[Continued in Balance of Power II]