What is Agency?
Just in case you have never heard of Counter Strike: Global Offensive, it's a hugely popular online FPS, successor to Counter Strike: Source and the original Counter Strike. The original came out in 1999 and the core gameplay has remained almost unchanged. Players are split into two teams and challenge each other in various game modes such as Bomb Defusal (one team has to plant and detonate the bomb while the other tries to stop them) and Hostage Rescue (one team must rescue the hostages whilst the other attempts to prevent that). The Bomb Defusal mode is by far the most popular, with maps designed with such detail that players can predict down to the second when another player is due to arrive in a certain area of the level. It's also the only mode played in competitive events and for huge prize money.
This leaves the poor Hostage Rescue mode sitting on the sidelines twiddling it's thumbs and feeling a little rejected. In part this is because the Hostage Rescue mode is far more of a roleplaying experience, often with very poor odds of success for the team tasked with doing the rescuing. Often the levels are designed in such a way that the defending team has a large positional advantage, where simply staying-put will give them a good chance of winning.
That's where we can start talking about Agency. Agency is a Hostage Rescue level, created as a collaboration between level designer Patrick Murphy, and myself doing the art. The basic idea being that Hostage Rescue could be just as precise and exciting as Bomb Defusal. It's been included in three official releases from the games creator, Valve, as part of their community level packs: Operation Bravo, Operation Phoenix and Operation Bloodhound. Phoenix being a community-voted choice, which was especially great to see that players enjoyed the style of gameplay and visuals that Agency brought with it.
In this article I will go over the process of creating the art, from props to set dressing, texture creation and lighting, while maintaining a visually pleasing aesthetic and serving to enhance the gameplay. This isn't a postmortem but rather a walk-through of the various stages, hopefully to give some ideas to others, with lessons learned both positive and negative.
Iteration from Whitebox to Final
Starting out you should always have an idea of what you're going to create, even if it is quite vague, as it'll point you in the right direction for both creating architectural spaces and letting your imagination fill in the blanks as you build the basic shapes of the level. We knew we were going to build an office space, but style was leaning towards an older government building with red bricks and musty wood. As I started to put in some basic textures we decided it felt too bland, and similar to other levels in the game. In order to stand out and create something really interesting and intriguing that would entice players to want to explore the level we decided to modernize the space and use white as the primary colour - this would help players see each other more easily and provide a striking visual setting it apart from other levels.
"Modern Office" is not exactly a style that has a single look, if you search for images you'll get back a lot of contrasting designs and ideas, trying to put every single one of those into a level would create a visual mess with no consistency. It's important to choose the right references for what you are building, something that looks cool in a single image or from a specific location might not fit into the theme of the level, and in a worst-case-scenario it might actually start to detract from the level as a whole. Trying to cram in as much content as possible simply makes your level feel less unified and jarring.
Unfortunately when you are presented with so many fantastic designs and ideas it can be hard to pick out what is important. After settling on the location: a modern advertising agency's office, I broke down the needs of the level into a few different categories:
The Area Specific content is "hero assets" for each location in the level. These are the things that help the player tell different areas apart from each other, a reception desk, a kitchen, a bathroom, etc. Assets that won't be used anywhere else except in their specific location.
Examples of Area Specific Content
The General Use content is the backbone of the building, it's wall sockets, ventilation tubes, sprinklers, desks and chairs. The things that could be used anywhere and would blend in to the background and not stand out unless you were specifically looking for them.
Examples of General Use Content
The Overall Theme content is what sells the theme of the level to players, advertising boards, company logos, large art installations and so on. These can be used everywhere but sparingly and should only be used as a subtle reminder to the player of where they are thematically. They shouldn't detract from the Area Specific content but should stand out more than the General Use content. This came in the form of abstract paintings, corporate logos, rotating advertisement panels and so on - things that would subtly tie the level together.
Once these categories were laid out, searching through reference images became much simpler as you know what you need and only have to find an interesting design or detail that enhances a specific category.
This isn't to say that everything was completely planned out or that development was flawless. Sticking to a plan only works until you open the editor, and if you try to force something you'll end up frustrated when it consistently fails to work. As an example we originally had the level set on the ground floor of a tall skyscraper. I spent a few weeks working on content for the ground but never really getting it to feel right within the theme of the level: the contrast between a dirty exterior street section and a spotless interior didn't feel right for the level, and felt a little too similar to another Counter Strike level. Patrick played around with some ideas and tried something I was afraid of: simply deleting everything I had done on the outside and adding an epic city vista. Instantly it felt right. The important thing to take away from this is that just because you have worked on something doesn't mean it's the right thing to be working on, and that getting input from other people with different ideas can vastly improve what you are working on.
The first mockup of Agency's rooftop exterior
The same space after an art pass
Another incredibly important thing I realised is making use of modular assets. If you are going to duplicate something in your particular modelling software you should ask yourself: is this efficient? Chances are you're just making things harder to change later and locking yourself into a particular shape; eg: a walkway has a railing around it, you model the entire railing as a single object. Now if you need to change that walkway a month later you're going to have to go back and change your railing model. It's better to create a smaller tiling mesh that can be used multiple times, as often you'll find you can use that model in other areas and in different ways than you had initially intended. You're simply applying the concept of tiling textures to models, and in the process saving yourself a lot of time.
A Believable Clean Art Style
Creating a clean environment can often be more difficult and time consuming than a very dirty and cluttered one, simply because any mistakes are magnified by the lack of other objects to disguise them. A room with a single chair in the middle is going to end up with the focus being on that chair, if you fill that room with a hundred chairs you're going to be less concerned with the details of the chair and more worried about why someone would fill a room with a hundred chairs.
In the modern office setting of Agency it would have made little sense to fill it with props and clutter, but a large empty space would just feel unfinished. A delicate balance of larger architectural shapes and smaller objects was needed. I like to think of this as functional art: it serves a purpose in the lore of the game world. Window and door frames, electrical sockets, thermostats and card swipes along with the maintenance apparatus of ventilation systems. These are the general use objects mentioned earlier, they fill out space and prevent an empty wall or ceiling from actually looking empty and at the same time they contribute to the believability of the level. It's important to think of the infrastructure of the building when placing these assets - if a wall has an air vent on it then the wall needs to be thick enough to support the ventilation pipes that feed it, Card swiping mechanisms need to be placed near doors at the correct height, electrical sockets should be placed logically in areas where they would be of use to the fictional inhabitants of the level and so on.
Several examples of functional art details
One of the most important things to do right when creating clean environments is to get the most out of the materials. It's not possible to cover every surface in dirt or decals, so the surfaces themselves become your way of showing detail.
For Agency this was achieved by making liberal use of the phong shading techniques in the Source engine for models, and cubemaps for world textures. Almost all models in the level have some amount of phong shading, and although it doesn't produce a completely physically accurate result it can be used to create materials and surfaces that look relatively accurate. Simply by increasing or decreasing the intensity of the phong amount allowed for a vast majority of the levels surfaces to be rendered accurately. As I didn't need to have a lot of noisy detail in the materials due to the clean style I simply used a small phong texture as a mask for 75% of the models and let the lighting and general shapes of the models do the rest of the work.
Simple phong shading to mimic real world materials
As most of the surfaces had a single layer of material, ie paint or coloured metal, the phong shading could be completely even without breaking the illusion; however some of the dirtier surfaces such ventilation tubes and water pipes had several layers: a painted metal surface with area peeled away to reveal with metal underneath or a layer of dust. These had specific masks that would enhance the different materials, and showing wear and tear in the background assets added an extra layer of depth without compromising the clean style.
Most of these textures were created with dDo, an excellent tool for quickly creating textures. I generally started with quite a dirty texture preset and toned down the details and noise until they were barely perceptible surface imperfections.
Agency features probably close to 95% custom art, and that's a lot of work for a single person. Using dDo allowed me to make a lot of content relatively quickly, and kept it all visually consistent.
The process of creating the assets with dDo was quite simple: first I modeled the basic ingame asset, then did a very quick and dirty placement of edge loops that allowed me to smooth the mesh and get a workable high poly. A very rough normal map was baked (along with a more solid ambient occlusion map), this rough normal map would never make it into the game, it was used purely for texturing with dDo. This rough-and-dirty technique was mostly used on the more general purpose assets that nobody would spend a lot of time looking at. For the objects that were in high traffic areas or that required finer detail a more robust normal map was created.
Tiling textures used throughout the world were photo-sourced and tiled in Photoshop. A few examples worth pointing out are the plaster wall textures and the marble floors:
The image above shows the ingame result, the diffuse texture, and the normal map of the standard plaster that is used throughout the level. The normal map was authored at 1024x1024 compared to the diffuse texture which was 512x512. I created several colour variations of the diffuse texture and for a very plain surface using a 1024x1024 diffuse didn't make much sense. The final touch was to add a subtle cubemap effect to bring out the normal map and add interesting coloured reflections in various areas.
Another example is a marble floor used throughout the level. The normal map is unrealistic in that it portrays an uneven bumpy surface when in fact it is more likely to be uniformly flat. However to break up the reflections and add some visual interest to such a large and empty area I added a subtle bumpy normal map which warps the reflections, but is subtle enough that it doesn't get picked up by the lighting and actually appear like a lumpy mess.
Good shading only gets you part of the way there, however. A poorly scaled model can break immersion instantly, especially when you are trying to create a believable real-world environment. There are tried-and-true metrics for Counter Strike so having a base to work from helped immensely, but these only give you a good starting point or a bounding box for your object. It's important to study real world reference and make sure your object is proportional to the world around it and also to itself. A unit in Hammer is an inch, so having wood that's 2 units thick, or a doorway that is 1.5m wide quickly makes things look wrong.
Working with Designer Blockouts, and not Destroying Gameplay
Agency was a collaboration, with Patrick doing the design work and me doing the visuals, this meant there was a lot of potential for overlap and working on the same areas, the potential for breaking things was huge.
Often when you create things as an individual you don't have to worry about version control or stepping on someone else's toes, however when you work with other people either for pleasure or business you, as an artist, need to change your mindset. You are not creating a portfolio piece but rather something functional that has to withstand hundreds of hours of real people playing it.
Your first role is to support the designer, and this benefits you as well. By creating the basic structures of the level: doorways, window frames, stairs, railings, cover objects etc, you are allowing them to work with the final assets and tweak gameplay according to those assets. Nothing needs to be finalized instantly, it's better to provide a rough mockup of the intended asset so the designer can play around with it and give feedback on the shape, size and silhouette. Once you are both confident it's going to work they can populate the level with these assets which saves you time in the long run, and once you finalize the model and textures they are going to be updated across the entire level without having to manually replace assets.
It can be difficult to determine exactly when you should start an art pass, especially when a level is constantly evolving. Rather than sitting idly by whilst Patrick was ironing out the design of the level I started on the creation of a few visual test levels to explore materials, lighting and modular assets. Once the first iterations of Agency were created, with rough shapes for important cover and controlling lines-of-sight. I went in and created an art pass and altered many of these original gameplay ideas, simply experimenting with different shapes and designs for the rooms. We had a constant dialogue and never considered something finalized just because it was finished. Playtests would determine whether an idea was valid or not in a way that speculation can only hope for. The most important lesson learned during this process of constant iteration was that work is very rarely wasted, and it is far more important to stay true to a gameplay ideal than to have an area that looks interesting in a screenshot but utterly fails when players get their hands on it. A box is a box is a box, it is down to you as an artist to imagine how that box can be interpreted within the context of the environment.
Initial art pass ideas for the central area (above) versus the end result (below)
Initial art pass ideas for the reception (above) versus the end result (below)
Initial art pass ideas for a hostage (above) versus the end result (below)
An important part of any environment is the lighting. Too contrasted and moody and it becomes hard to identify players, too bright and monotone and it becomes boring and a strain on the eyes. For Agency I used a series of instanced lighting setups: a model to visualise the light source, a spot light to direct the light, and a sprite or light cone to add a visual effect around the light. Each light setup was unique to the type of model used for the actual light source, ie: all spotlights were identical, all fluorescent lights were identical etc. This meant I could change a single light and have the others update automatically, and always get an accurate result.
Then it was just a case of placing these different types of lights where they logically made sense in the environment, and if an area was too dark an appropriate light source was added, and if an area was too bright lights could be moved around or removed entirely. This made it quite easy to light as everything was guided by reality, which has plenty of reference material, and had the side effect of helping to make the environment more believable. By using various colours on the floor and walls I could direct lights towards them and take advantage of the Source engine's excellent radiosity and spread interesting colours to nearby surfaces.
In many areas the ceiling was opened up to reveal the sky and to let natural sunlight into the interior spaces, this was done to provide contrast to the electrical lights and to get extra radiosity bounces into the environment. Some areas had lights removed or toned down to allow other more important gameplay areas to stand out, for example the image below shows how the corridor here was darkened both by using darker textures and by using restrained lighting to make the room in the distance appear brighter as this is an area that enemy players will appear from.
This could have been taken even further by possibly using emergency exit signs to add hints of colour to important gameplay areas and chokepoints. A consistent lighting language would have helped guide players during the first few times playing the level. There are some large open spaces that would have benefited from some coloured screens or lighting panels, or possibly making some of the larger glass surfaces tinted, to add a little extra colour and prevent such a monotone look whilst not being over-bearing or detracting from the realistic style of lighting I was aiming for.
During the course of developing Agency I had a chance to learn a few things and come out the other end a, hopefully, better artist.
So, what went well?
The iteration process never had any hiccups, by using modular content and being prepared to discard ideas and art styles that weren't working we ended up with a better level. If we had tried to force the original idea of a ground-level government office we would have ended up with a completely different level, complete with underground parking lots and elevator shafts. Exciting stuff!
The power of iteration cannot be understated, and understanding that a mockup or a blockout of a level is simply a temporary phase that doesn't represent the end result. Areas changed drastically between versions, sometimes due to design requirements, and sometimes of shifts in art style; but each version was better than the last, more refined and polished.
What went less well?
In direct contrast to the statement above, sometimes the iteration interfered with more important tasks. I got stuck on areas trying to get them to work instead of letting them sit for a while and returning to them later. I tried to force an idea for the exterior part of the level and it never felt right and consumed way too much time, when all it took was getting some outside perspective. Luckily during the process I learnt to trust designers when it comes to art, just because they might not build high poly meshes doesn't mean they aren't artistic.
Another problem was building too much content completely unique for an area which meant when we inevitably changed things it became time consuming to shift assets around, and makes it less easy for others to re-use that content without creating an almost replica of the area it was designed for. These unique assets helped sell the realism of the level but made them harder to work with.
Hopefully this has been interesting and insightful!
This article may contain slight spoilers
DOOM's Argent Tower is a superb Single-Player level. The Argent Tower motivates players with an obvious goal, expands in scope (almost unbelievably), and masterfully controls pacing. A playground for new a ability and a giant environmental puzzle, the Argent Tower is the best level in this excellent reboot of the franchise.
Now, let's explore the reasons why this level feels so memorable!
Players will know their goal from the outset: climbing the Argent Tower. In addition to verbal instructions, the level's construction and composition never fails to aim you upward. Warm lighting moves up vertically, so that players' eyes are always drawn upwards.
Even the item you acquire in the level's prelude is a double-jump upgrade, which the level then associates with an oft-repeated green light motif. Players will be doing a LOT of double-jumping in the Tower, so the game articulates a method to guide them.
While players may or may not consciously respond to this green-light motif, the designers clearly believe it works as a navigational aid: it is repeated with brutal consistency throughout the level.
When players reach the Tower's inner core, the vast power of DOOM's engine is indisputable. Great music kicks in, monsters spawn all around the player, and the game "gates" engagements without muddying players' central, long-term gameplay goal.
The symmetrical, circular design of the Tower's core proves extremely useful in several respects. Because players can only progress upwards, they get to experience fun combat engagements and jumping puzzles before they are neatly stuffed into small corridors adjoining the main core.
This contrast between the core's verticality and its cramped side passages makes for easily controlled progression through the level and amplifies the awe of returning to the core. In one side area of the Argent Tower, players experience a "monster closet" ambush, a classic DOOM design trope in which a demon emerges from a closet adjacent to a corridor. Here, the designers chose an exploding demon for extra "oomph"!
There's just something timeless about monster closets. That the game dives down to its most granular level (the monster closet) additionally provides contrast to the heights of the massive core.
DOOM carefully reminds players of their progress ascending the Tower. In one cramped side-area, players are faced with the seemingly trivial task of shooting canisters that underpin an elevator blocking their path. After destroying the canisters, the elevator falls down its shaft.
Half-Life 2 used similar imagery to convey the scale (and ongoing destruction) of The Citadel:
An additional point of this elevator diversion was to slow players down, to keep them away from the showpiece core a little while longer.
New players will take a minute to identify the canisters overhead and discern that they need to be destroyed, because this is a novel task and because FPS players notoriously fail to look upward. Later in the game, the designers repeat the canister mechanic before providing players the BFG, the defining weapon of the series. Without the subtle change in momentum the canisters provide, gaining access to the Tower's rooftop or the BFG would feel too straightforward and simplistic.
Having artificially lengthened the break players take from the core, the designers have guaranteed that environmental contrast will enhance perception of the Tower's scale AND that player intelligence and momentum has been challenged by a new problem. (...but because this is DOOM, problem solving is still ultimately about destroying shit.)
Players complete more than six different jumping tasks including riding a flying drone to climb the Argent Tower and enter a portal into Hell.
Such a variety of jumping puzzles and hazards makes the level memorable and is another technique enlarging perception of the Tower. To be clear, jumping puzzles are universally terrible in every FPS game, but their annoyance here is dulled by the focused grandiosity of the level and the ability to grapple onto ledges. The designers ultimately cared a lot more about giving players a memorable locale than sparing them falling deaths.
After reaching the top of the Argent Tower, players are greeted by a giant, climactic battle which ends with a wonderful fade to white.
Only now are players ready to enter Hell confident that they've truly gotten to experience Mars.
It's important to remember that, fundamentally, the Argent Tower is about going from point A (the foot of the tower) to point B (the top). Faced with a similar Tower-landmark, some designers might path this route with nothing more than a simple elevator cinematic or miss countless opportunities to do something special. DOOM's designers, however, missed nothing: they recognized the need to offer players dense and varied challenges, careful pacing, and spatial design rich with contrast.
Later, when players return to Mars, the destroyed husk of the Tower provides an instantly recognizable landmark re-orienting players on their adventure and a tantalizing hint that things are different now.
The Argent Tower goes to show that great levels are not about the destination, but the journey -- and all the controlled chaos along the way!
Thanks for reading!
Titanfall 2 was one of the best FPS titles of 2016, featuring a very strong single-player campaign with interesting combat and puzzle gameplay for both players and their Titan. Additionally, each level featured its own special twist: "Effect and Cause", for example, presents players with a memorable time-traveling mechanic.
The time-travel mechanics of "Effects and Cause" serve couple of purposes, influencing not only the way players traverse the environment and its associated obstacles, but also how they fight through the level's combat scenarios. Two different time periods are a threat to the player, so the designers decided to allow players to see where the enemies from the past are located.
Once you move from past to the present, enemies leave a small blue particle in the place where they had been standing. Although the effect lasts no longer than two seconds, it’s enough to help players plan their next move. This twist on encounters makes them much more interesting and dynamic.
For "Effect and Cause", the developers created distinct enemies archetypes with different engagement distances and attacks for each time period. In the present (a destroyed version of the map) the player deals with robots and wildlife. In the past, players face armed guards in the facility. Eliminating the danger in one reality does not make it disappear in the other, forcing players to think constantly about their position versus the enemies in the different time frames.
Let’s discuss three selected encounters from "Effects and Cause" in-depth to see how they work in action!
The first encounter where players freely use the time-shift mechanic starts shortly after players exit a lab area. Here, enemies are located only in the past, when the facility is operating and functional. This prevents players from becoming overwhelmed with two types of enemies in two different realities within the first big encounter of the level.
This encounter is set up in two distinct spaces. The first space is a big room with a single entry point in the form of a double door opened by a panel, with combat focused at the far end of the room. The second space is a large corridor with a pocket in the middle and a security room at the end. A panel in the security room must be used in order for the player to progress.
Both encounter spaces are divided by a time-shift puzzle, the only way to continue onto the next arena. This time-shift puzzle serves as combat gating and also adds variety to encounters that are otherwise only about shooting. The gating also teaches the player that some spaces cannot be traversed in any time period, and that the only solution to the obstacle is to find alternative routes.
There are eleven enemies in this encounter: four located in the first room, and seven in the second room. Once you eliminate the two enemies in the first room, the remaining two enemies get into position. The second space has a fixed number of soldiers, with no additional waves. All the soldiers are using guns or rifles. The advantage/challenge to the player in this encounter comes from the number of the enemies, not their abilities.
Once the player enters the first space, they see two soldiers talking to each other. It’s up to player to start the fight and pick their preferred attack method. Once the first two enemies are eliminated, players enter an area with clearly defined architecture and a no-man’s-land inbetween. Players should also see a weapon lying on the desk, a gameplay "carrot" which helps to draw players into the fight. The enemies will hold their positions and try to shoot the player from behind the safety of cover.
The second area gives players more options, and also allows them to scan the area earlier (both from the first room through the lasers, and also from a vent). The designers ramp up the difficulty here, introducing more enemies into a tighter space.
With the time-switching mechanics at hand, players can prioritize threats in order to set up their own tactics. It’s clearly up to player how to plan and play this encounter. As there is no threat in the past timeline, players can experiment with going back in time without punishment, ‘escaping’ the combat at any given moment in order to reload, reposition and jump back to the action. This encounter is memorable as it is the first time that players fully use their time switching mechanic, functioning as a safe environment to learn. In other words, it's a skill check and a preparation for what lies ahead...
The second encounter worth analysis is much more varied with how it positions enemies throughout the level. It also places enemies in both time periods, serving as a playground for prioritization strategies and other interesting player tactics. This encounter also features more verticality, which helps prevent players from feeling too overwhelmed with enemy forces, while also allowing players to use more of their Titan-piloting skills.
This encounter is located in a fairly large room with ample verticality. Players enter the space on the upper floor through a single entry point and continue their way onto a balcony, letting players familiarize themselves with the space from above. At the far end of the room, players will spot a staircase going down to the lower level where elevators are located. This area has two big areas of standing cover, accessible on both heights, and a variety of crouch-height cover such as railings, desks and potted plants. This space also has a small side-room allowing further tactical options. This whole area is gated with an elevator door which does not open until the combat encounter is over.
This encounter is quite varied in terms of the enemies players face. In the past timeline, players face eleven soldiers: nine regular soldiers and two heavy soldiers with shields. These soldiers come in four groups of two or three each. The solders come with short intervals inbetween each wave, so that the player has time to react and make more intellectual choices.
In the present, players face three robots appearing almost at once when they walk along the balcony at the top of the space. Once the player goes down, they have to fight four prowlers which appear one after another with a couple of seconds delay between each new spawn.
We start the encounter in the present timeline, with the gate blocked in the past timeline. On the way to the staircase, three enemy robots spawn but do not pose a big threat to players. Once players move down, their attention is drawn to a desk with guns. This helps players to immediately position into a location in front of the elevators.
Once players shift to the past, enemies start to appear from the elevators. There is not enough cover to fight off all of the attackers, forcing players to prioritize and switch in time to better position themselves for attack. Once players go back into the present, prowler enemies will start to appear, forcing players to continue constant movement.
This encounter may feel a bit hectic, but it is a good test of both pilot skills and thoughtful time switching. It's the first encounter which forces players to prioritize which enemies they want to deal with first in different time periods. Due to the designer's smart use of the elevators, vents, and robot storage, enemies are brought into the field in an interesting way. But at the same time, enemies are introduced to the player with clear sound and visual cues, so they remain alert to upcoming surprises.
The third encounter I want to breakdown is by far the most robust yet. It features different height levels, space divided into two areas, and flanking paths which can be accessed only through certain time periods. It serves as the "final skill check" for all of the pilot abilities and time-shifting gathered thus far in "Effect and Cause".
This encounter is spread across two areas of vertical space, connected by multiple paths that create nice loops for players to use to their advantage. There is one clear entry point with a wide view of the whole combat space and one exit located in the second area, but the space inbetween offers a great deal of choice in terms of how players can tackle the encounter.
Playing through the encounter, players will learn that there is a geometry difference between the two different time frames that can be overcome with some of the pilot skills at their disposal. A big catwalk goes around the whole room with additional rooms with guns and ammo on the bottom level, for example. The amount of space available is needed, because the combat space is packed with enemies.
In the past, players have to fight twelve soldiers: nine regular soldiers and three heavies with shields, as well as three robots. The enemies are spread out across the whole space of the encounter, but because the areas are connected with each other through multiple paths, the enemies will try to chase and eliminate the player. This means that the encounter feels very dynamic and tense.
In the present, players face robots: eight prowlers inside, and even more of them outside fighting with BT (the player's Titan). The enemies in the present are hostile to each other, showing players an example of how the enemy AI can actually fighting eachother: information which players can then use to their advantage.
Players enter this area in the past, where they witness a single back-facing enemy, instantly inviting them to perform a takedown. From this point, the encounter is very open to experimentation: the player can either continue in the past and fight a big wave of soldiers coming through the main path (a staircase in the middle), or they can switch to the present, where they will find open flanking paths on both sides of the level. Going with the latter option offers a moment to breathe before prowlers are spawned, but it will also disable an ammo dispenser in the first area, adding consequence to player choices.
Staying in one place will result in a massive pile-up of enemies in the area, so players are motivated to move around a lot, time shifting when needed. The second area of this encounter is one of the level's biggest in-door combat spaces. If players choose to go into this second area in the past, the encounter will be quite vertical with soldiers located both on the ground and on the upper catwalk. Switching to the present will cause a bigger concentration of enemies on the ground floor.
Players are given enough space to fully use pilot’s zip-line ability to create shortcuts across the room, accessing the various loops and ammo dispensers needed to create a fair fight despite overwhelming enemy forces. There are very few conditions placed upon this encounter, so players can leave the area and jump into his Titan to deal with different threats at any time. Overall, this encounter serves as a test of everything learned previously, with players having the option to ‘lower’ the difficulty of the encounter using their titan.
The above examples are just a slice of Titanfall 2 gameplay contained within the excellent level "Effects and Cause", but in my opinion clearly shows how this great game was enhanced by its time shifting mechanic. The idea is fairly simple: time-shifting is nothing more than teleportation between two different levels, one layered on top of another, but the strong execution makes for a memorable experience that really stands out in comparison with other shooters. I highly recommend playing "Effects and Cause" as it is both challenging and fun, a level where Titanfall 2's time-shift mechanics comes into focus, providing additional depth to the whole game.