Here's our case study game scenario:

You're a police captain in an elite unit. You fight back the provoked and angry mob that is trying to kill Jason Falconer, a prisoner you're guarding.

He's been accused of treason, and they want him drawn and quartered. Not that you like Falconer—but guarding him is your job.

After the fight, one of your lieutenants tells you he's never seen anyone fight like that, and that he's glad to serve under you. My guess is you'll like that junior officer. We all love admiration, and thus this builds Chemistry.

Can an NPC have insight into you? It certainly sounds impossible. But let's see….

You have to transport Falconer across town at night in an armed jeep.

But a lot of people want to get at Falconer, and the cross-city journey deteriorates into one hair-raising battle after another. Bullets fly, blood splatters. The route you took was supposed to be secret. There's no way the mob could have known your plans.

One of your would-be killers, now dying on the cold city pavement from your merciless onslaught of lead, spills the beans:

The reason that this hoodlum armada knew where to repeatedly ambush you is that one of your own men, a lieutenant named McCully, purposely leaked your route.

Now understand, McCully had been a friend of yours until now. You went out on missions together, and he even risked his life for you once. So, when you learn he's a turncoat, it comes as a total shock.

The harrowing cross-town mission continues. Barely alive, you make it to the jail where Falconer will be guarded (for his own protection). Your officers there have already heard how McCully sold out you and the unit.

One of them approaches, looks at your ragged condition, and comments, disgustedly, “McCully, can you believe it? After what you guys have been through….”

And that's exactly the way you feel. The fact that what you're feeling is acknowledged by this fellow officer creates chemistry between you two.

You just risked your life to get Falconer across town.

Falconer (who up until now you assumed was guilty) explains why his enemies in the government framed him for treason and want him killed: He knows their plans.

They're going to instigate riots in several cities simultaneously, and then use these riots as an excuse to declare martial law. Once martial law is declared, they'll use the “state of emergency” as a reason to round up all their opponents and have them imprisoned or killed.

You give yourself the mission to search out corroborating evidence, which you find. Falconer was telling the truth.

So now you're off on a mission to locate the compound where the secret plans to instigate a national state of emergency are hidden. This compound is the base from which the entire conspiracy is organized.

You need to find the compound and retrieve those written plans—the “smoking gun”—so you can bring them to the press and expose the conspiracy.

One minor setback: You don't know the location of the compound. You know someone who does, however, and that's your “friend,” McCully, who earlier betrayed you. So you set off to capture him.

One of your men, a young rookie, volunteers to help you. He joined the force to “Serve and Protect,” and he believes in those ideals. The notion of police being used as a tool for those who would abuse power is more than he can take.

So he joins you on this next mission. What you two have in common, of course, is your similar feelings about what's right and wrong.

You locate McCully, the cop who betrayed you, in a complex outside of town. You and the rookie sneak in, but soon guards swarm you and an intense firefight erupts.

At a certain point in the battle, when you're outgunned, the rookie tosses you a powerful automatic weapon (one you've used before so you know the controls). You catch the gun—it comes just at the right time, and its firepower allows you to blast your way through this assault and complete the mission.

Trust me, you'll have chemistry with the rookie.

Let's return to our story about Falconer and the conspiracy to instigate riots in order to justify the declaration of martial law. You had just fought with McCully, and retrieved the information as to the location of the compound in which the conspirators are using as a base of operations and in which their plans are kept.

Now there's a further twist: Falconer's 10-year-old daughter is being held prisoner in the compound. It's his former bosses' way of making sure Falconer doesn't betray them. If he does, she'll be killed. He's terrified this will happen. He shows you her picture. She looks beautiful, innocent, and playful.

You have to get into that compound, rescue Falconer's daughter, and find the plans to trigger that state of emergency. Armed with this evidence, you can then provide concrete proof to your superiors and stave off this disaster—or so you think, until you discover that they too are part of the conspiracy. And the clock is ticking….

If you choose to save Falconer's daughter and not just go for the plans, you'll be facing a much greater risk.

And there are other consequences if you go on this mission. You might get tried for treason, just like Falconer. You will, at the least:

All this is made quite clear to you. And it's not just that all these losses will come in a closing cinematic—you'll have to finish out the game in that state of privation and disrepute.

To effectively pull this off in the game, we might want to set up two alternative endings. If you're the player and you don't want to infiltrate the compound, there would be some big boss fight to serve as the game's finale.

But if you decide to risk it all, the question is, will this just be another mission, or will the experience have any emotional impact on you?

If you've really come to like, respect, and care about Falconer, and thus care about his daughter…

And if you really like the rank, weapons, and respect you get in your current job but which will all be sacrificed if you take this mission…

Then this won't be a mere mission. The decision should be difficult to make. But if you make it, you'll feel noble and heroic.

Emotion could be further heightened in the following way: Once you fight your way into the compound, you break into the heavily guarded room where the girl is being held. You're entering the room triggers a scripted sequence that makes it seem as if you arrived just as if she was about to be killed by a guard with a long knife.

However, you get creamed. First of all, in that room is a sub-boss who beat you earlier in the game and left you barely alive. Because of his rain of bullets, and because of extremely heavy gunfire from another man in the room, you're forced to retreat or get killed. The game leaves you no other option.

Your retreating triggers another scripted sequence: A few seconds after you back out of the room, you hear the girl's terrified scream, as if she had just been cut (which indeed she has).

You'll definitely be weary, and maybe even a bit afraid of going into the room a second time, for fear of dying. After all, earlier in the game you learned that your nemesis in that room is actually a better fighter than you are. Additionally, you almost got killed a minute ago.

These factors, coupled with the fact that saving the girl is optional, would make the choice to go back into that room truly a heroic one, because you know the mission to save the girl is not necessary—only collecting the data is. You can walk away from this dangerous situation, and if you choose to fight (and save the girl who's screaming in pain), you're likely to be very emotionally rooted in the situation.

What are you going to do? You need to charge back in, but this time the game allows you to be victorious, if you're very skilled with your weapons—although you wouldn't know that victory is possible when you blast your way in, because the previous time you were in the room you would have been killed if you tried to rescue the girl.

In this hypothetical game, I've introduced the idea of self-sacrifice for a higher causes (or causes) to force the player to become a better person. The causes were:

It should be noted that stopping the conspiracy is the least emotional of these causes. This can be fixed, however, if earlier in the game, you have gotten to know and really like a person or people who will be hurt or killed if the conspiracy goes forward. Liking this person or these people would come from their having Rooting Interest, as well as the use of NPC Toward Player Chemistry Techniques.

If you're the player, let's look at the sacrifices you'll make if you decide to rescue Falconer's daughter. You will:

In life, almost any taking of responsibility for anything or anyone requires some kind of sacrifice. Here, the sacrifices have been multiplied and heightened. If you, the player, care about Falconer, and you risk or accept these sacrifices, you'll feel like a better person at the end, just as players who finished Ico did.

The game shouldn't end after this mission. The player should be forced to live with the consequences of his or her choice.

So, let's say you save the girl. You're not tried for treason, but all the other horrible consequences you were warned of do unfold. You're fired, your weapons are taken from you, and the public scorns you as being anti-American.

Now comes the final boss fight—against the man in charge of the entire conspiracy. And you have to go into it with just one lousy gun.

So the consequences you suffer aren't just revealed in a final cinematic, but are woven into the gameplay itself.

The fight begins inside a security installation and you're vastly outgunned. It's all you can do to hide and dodge bullets to stay alive, because your opponent is like an enraged, walking weapons depot on steroids. At best, perhaps you get off an occasional shot that forces him to retreat a little.

But if he retreats just enough, this allows you to finally make it to a weapons cache, where you can grab all the firepower you want. Now that you're loaded for bear, the real fight begins.

Why give you so many weapons at this point? First, you've already made the sacrifice and experienced the consequences, so that plot twist has been milked. Most importantly, we don't want to deprive you of a great boss fight at the end.

By the way, if you were designing this game, there are two ways you could end it. The first is that the evidence you retrieve about the conspiracy hits the press. Belatedly, after first being accused of treason, you're redeemed in the eyes of the public, all the conspirators are brought down, and you get your old job back.

Or, you could end it in a much darker way. You've foiled the conspiracy and killed the man at its head. All the others who were involved retreat into the woodwork. But the public never knows what occurred and of all the good you did. Instead, although you're not tried for treason, you are nonetheless painted as a traitor in the eyes of the citizenry.

There are a few people, though, who know what a hero you are. And that's Falconer, his daughter, and a handful of others who are overwhelmed by your bravery and integrity.

Which ending is preferable? Arguments could be made for either one. It's a matter of taste and artistic judgment. Which ending would you choose?

In these last two chapters, we've focused on ways to cause players to bond with NPCs. Chapter 2.10 detailed a few methods to make a player identify with an NPC. This chapter dealt with techniques to make a player feel close to (i.e., have Chemistry with) an NPC:

Certainly our emotional immersion in life is enhanced by the existence of people with whom we feel close. Emotional immersion in a game can be significantly enhanced from a player feeling close to one or more of the game's NPCs.