During the development of Rage, I was principle designer on a level known as 'Blue-Line Station'. This level is fairly unique, for, it is the only main story-line level comprised solely of mutants: a swift, group-oriented, melee-centric AI-type. In the analysis below, I will outline the unique challenges that this presented and the methods by which I attempted to overcome them.

Part 1:

Building Suspense

When planning a bandit encounter, it was always fairly easy to derive an appropriate setup. Being as they were human AI, the player expects that in any context they are exhibiting fairly predictable human behavior (patrolling, talking, working, etc.). Additionally, the ability to observe the bandit's type and position within the combat space was ideal, because it provided the information needed to plan the method by which the player would initiate combat. The player knows, in a general sense, how the bandits within a space will react at the point combat is initiated, and how they will react to the player's actions as the combat unfolds. Ultimately, the bandit combat loop is a calculated, medium-paced game of chess that rewards the player for behaving logically and anticipating the AI's tactical behavior pattern.

Planning a mutant encounter, on the other hand, requires quite an opposite approach. Mutants do not tactically utilize the combat space, rather, they rush straight at the player and attack. Consequently, being aware of their relative positions ahead of time does not give any advantage to the player. Additionally, mutants are designed to inspire fear; their origin and motivations are largely mysterious. Therefor, the best course of action is to utilize this element of fear and mystery, building it up until the moment the encounter begins, at which point the mutants explode into the combat space. That is to say, since the mutant combat loop in and of itself doesn't require the player to apply themselves intellectually, the enjoyment of the combat to some degree depends on the anticipation building up to the combat. This is most effectively executed by stringing together a number of what I call 'pre-combat encounters'. These are non-combat encounters which serve to foreshadow the fight, building the tension of the player to the appropriate threshold before breaking that tension with the genesis of actual combat. Pre-combat encounters entail anything that makes the player aware of a malevolent mutant presence. In the following example, I use a string of pre-combat encounters to reinforce the idea that the indigenous mutant population is staging an ambush. This is achieved by a string of sighting, in which the player happens upon a mutant which becomes startled and escapes out of sight. These sightings are gradually complemented by distant shrieks and howls, followed by small groups of mutants moving swiftly in the distance as if they are converging at some unknown point, lying in wait for the player.

The main problem with staging these encounters is that there is no foolproof way to ensure that the player will actually see them unfold. This can be mitigated to some degree by tying them to look-triggers, but there is still no guarantee that the player will be facing in the direction of the encounter long enough to observe it play out. Through testing, I calculated that the player on average will witness roughly 70% of pre-combat encounters within a space. That being known, my strategy was to craft 30% more encounters than what I considered ideal. This way, witnessing 70% of these encounters becomes the ideal. The gallery below steps through each of these encounters in the first section of Blue Line Station, showing the player's relative position to the mutants involved.

Pre-combat (0:00 - 3:20)

Part 2:

Controlling Chaos

Mutants have the ability to emerge from small cracks in floors and walls. Given the post-apocalyptic setting of Rage, the designer has license to place spawn points almost anywhere within the environment. This is one of the biggest advantages of working with mutants; unfortunately, as it turns out, it is also one of the biggest challenges.

One of the most frustrating aspects of fighting groups of melee AI is introducing them into the scene in a manner that prevents the player from being blindsided. Feeling as if you're overcoming a potentially overwhelming situation is exciting; In contrast, actually being in an overwhelming situation is frustrating. That being known, the ultimate goal is to innovate ways that serve to create the feeling of insurmountable, imminent danger while giving the player a subtle, hidden advantage that helps mitigate the actual threat. The innovation I came up with that best mitigated the threat posed by groups of mutants is known as "dynamic directional spawning".

Dynamic directional spawning is a way to create the feeling of a overwhelming odds without making the combat unmanageable. It allows wave after wave of mutants to perpetually spawn without putting the player in a position where they're not aware of the threat present within the space. Similar to pre-combat, the trick to this system is based on the utilization of look triggers. As an example, let's look at the first combat in Blue-Line Station that utilizes this system. It occurs shortly after the first ambush in the terminal below. The terminal is a relatively large open space with mutant entrance-holes covering the floor and walls. As the player enters the space, the first group of mutants spawn in front of them. The player has room to move on the left and right, which allows them to move laterally through the space without risk of becoming cornered. As the first group of mutants begin to die, the dynamic directional spawn function becomes active. Let's say that, within the function, we define the maximum amount of active mutants as "5". As soon as the function detects that the number of active mutants has dropped below 5, it will spawn the number of mutants necessary to bring the number back up to 5. However, these mutants wont spawn just anywhere - spawning mutants randomly inevitably results in the player being blindsided, which decreases their situational confidence and from that point forward distracts their attention away from the threat in front of them. Rather, the additional mutants will always spawn from points within the player's line of sight. Consequently, as the player moves around the combat area in an effort to keep a safe distance between themselves and the enemy, they are constantly witnessing mutants enter the scene in front of them. The advantages of this system are twofold. The player witnesses each new addition to the mutant horde, which gives them the prerequisite knowledge of the situation needed to intelligently determine their next course of action. Additionally, is ensures that the mutants' unique entrance animations are not wasted. The player is granted the enjoyment of watching the unique way in which the mutants creep into the space through their respective cracks.

The system is subtle enough to not gain the player's attention; in my experience, they are generally unaware of it. As a result, it feels as if mutants are spawning all around them, which adds a critical element of anxiety without the detrimental affect of mutants actually spawning all around them.

Encounter Beginning

The player enters the space. A number of mutant spawn-cracks are visible within the area.

Part 1: Combat Initiation

As the player approaches the floor of the terminal, the first group of mutants enter the space via floor and wall spawn points. Not wanting to become cornered, the player begins strafing through the space to ensure that there is room for evasive action whenever it's necessary.

Part 2: Reinforcements

As the player continues to move and mutants begin to die, additional mutants begin to enter the space in the direction in which the player is looking. Mutants will always appear in front of the player. This way, the player is always aware of the number and position of mutants; the player will become aware of this fact on some level, conscious or unconscious, and will therefor wield the confidence to focus on the threat in front of him instead of worrying about an attack from behind.

Part 3: Situational Confidence

If the player does get attacked from behind, they will attribute it to their failure to keep the enemy in front of them as opposed to blaming the game for spawning them in an unfair position.

Step 4: Ancillary threat

As the player gains comfort with the space and the native combat loop, a grenade-throwing mutant appears on a ledge above the combat area, throwing grenades down at the player. This serves to inspire even more player movement, and adds a threat that the player can engage in two ways. One way is to make this grenade mutant their primary target, dispatching it as quickly as possible before switching attention back to the mutants within the immediate combat space. The other way is to allow the grenade mutant to survive for the time being and attempt to shepherd the other mutants toward the grenades.

Step 5: Introducing Variation

After a predetermined number of mutants have been killed, there is a temporary pause in the perpetual spawn loop. As soon as the player looks in the direction of the exit stairs, a group of three mutants appear from out of sight and run down said stairs toward the player. The mutant in the middle is a "dyno-mutant" - a mutant wielding two sticks of lit dynamite that explodes on death or once the player is within the blast-radius of their dynamite. Ample time is given for the player to process this threat, at which point the perpetual mutant spawn begins again. Similar to the grenade-mutant, the player will make a decision whether to dispatch the dyno-mutant immediately or to risk keeping them alive in order to use them for their own ends. This dyno-mutant interjection occurs twice during the battle.

Part 6: Additional Variation

After the dyno-mutant threat has subsided, a scoop-mutant appears on the stairs and begins to hurl their projectiles toward the player. This serves a similar purpose to the original grenade mutant, but the location and method of attack are different which keep the concept fresh.

Mutant combat loop (6:55 - 8:20)

Part 3:

Conclusion/Takeaways

After developing the 'dynamic directional spawning' system and refining best-practices for pre-combat implementation, I duplicated these methods in 'Abandoned Distillery' and the entirety of the 'Wasteland Sewers' DLC with similar success. I believe the principles behind these concepts have the potential for broad application. None of these ideas are by any means groundbreaking. Rather, they prove that simple concepts brought to their logical conclusion within the framework of a game's design can make a huge difference. At the end of the day, the key to successful design is thoughtful analysis of a system's limitations. Once one has a firm grasp of these limitations it becomes much easier to derive simple, elegant solutions.

James Selen

Designer/Scripter