Level Design Primer: Notes on Playtesting

Playtesting is like working out--you can go a long time telling yourself you don't need it, and then when you finally get around to doing it it will hurt so much you'll probably stop again for too long.
But resist the temptation to quit. Understand that testing is an inextricable part of good design; what you're making is for the player after all.


You Are Not Your Work

I feel a little silly parroting this again, but it's worth it if gets through to just a few more people. Remember the lesson of every teary-eyed critique in art classes the world over--you are not your work.
It is of you, but it is not you. While you may be deeply invested in it, once you have made something it is out there in the world and separate from you. No matter how coarsely phrased a criticism may be, remember it is a reflection of the work and not you personally.
There are creative professionals that get by without learning this but boy does it cause them no end of grief. The pride and joy of creation I think must necessarily follow with detachment; a distanced, even clinical appraisal.
While I've found this kind of professional detachment also tends to shave the peaks of euphoric highs during development, it's more than worth it by pulling out of the gutting lows. You can be still be passionate and excited about your work without taking the emotional rollercoaster that comes from not being able to separate your work from yourself.


Conducting The Test

[This is assuming you're using what Will Wright calls a "Kleenex tester," a player without prior experience with the game who will likely not test again, rather than a professional or regular tester.]

Make sure your tester feels comfortable enough to talk freely, but do not get too friendly with them. Exerting the social pressures of a new acquaintance (or invoking your friendship with someone you know) means getting polite answers instead of useful ones. People will likely downplay or politely lie to your face to avoid an uncomfortable situation.

I usually start with a very short capsule summary of the game and it's premise (no more than a few sentences), along with any mission-critical info if they they're playing a level that's not the beginning of the game. I also make sure they are able to set any control preferences before they begin (though I don't know why we tolerate your kind, EDSFers. Go back to the Moon.)

Then it's time to prime the tester to think outloud. I'll say something like the following:

"What I'd like you to do is say anything that comes to mind while you're playing, things like "I'm frustrated," or "this part is cool."  Don't worry about offending me. If something is really bad you're doing me a favor by mentioning it, it'll help make the game better. Ask questions if they come up while you're playing, or if something isn't clear say so and I'll respond to everything--but after the test is over. While you're playing just enjoy yourself, pretend I'm not here."

Be very aware of how much physical positioning factors into the tester's comfort level. Grab your notebook and sit several feet back, as far back as you can off to the side and well outside their peripheral vision. Making sure they don't feel like you're hovering is important--nobody likes that feeling, and testing can already feel a little weird for most people already. Giving the player headphones can also help them feel less self-conscious. You can still come up and fix a show-stopping flaw or restart the level as necessary, but generally try to make yourself invisible for the duration of the test. You're there to observe.


Slow Motion Trainwreck

And here comes the hard part. Now you get to see all your brilliant plans laid to ruin as what you thought was simple and straightforward to the player is anything but. Try to take it in stride; now when I playtest I almost feel like a classic Freudian analyst, or a scientist regarding a lab trial. Clinical detachment is useful here.

Once the level is out of your hands there's nothing you can do to help it if something goes wrong. So if during the playtest something does happen (such as the surprisingly common scourge of "player error"), short of a crash or other complete show-stopper, you're just going to have to grin and bear it. This can be one of the most punishing aspects of a playtest but this is your lot. What's hardest to take often ends up the most useful information.

So pay close attention. Get impressions down immediately, but make as many notations about specific problems as you can. Missed cues, objectives that are ignored or unseen, key dialogue that doesn't seem to be heeded, horribly unfair firefight, collision problems, the player wandering off the map--all of the above might happen in a single test.
    This is your chance to see your world through someone else's perspective, so keep your eyes on the screen and write down any comments they make. Make a mental record of where they're looking--if there's an important element that never crossed their sightline, why or how did it happen? Did you misjudge the clarity of your layout?
As we talked about in the previous LDP article, no one tester's word is law, their experience necessarily represents just a single small data point. Yes, a single test can reveal a lot of issues that obviously should be fixed, but generally speaking you're looking for patterns from multiple sessions; reworking too much based on a single test can be very counter-productive. Balance your observations with instinct.

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Regular testing will likely result in a greater knowledge of your own bias/hyperawareness of the level. What you feel like is "really overdoing it" might just be noticeable to the player, and the touches you consider "subtle" will probably escape notice entirely.
So test early, test often--it will get easier, and you'll have to redo so much less work if you get playtesters in at the earliest opportunity. Your sense of what works and what doesn't will naturally sharpen. You'll find yourself building level elements that anticipate typical player behaviors, rather than having to come and fix them after a test.

Level Design Primer: Starting A New Level

When a modern FPS level takes weeks or months of production time it's probably a good idea to approach a new one with care. What follows is a summary of the six most important lessons I've learned so far about starting new levels.

1. Plan On Paper

"It is important to use your hands, this is what distinguishes you from a cow or a computer operator."
- Paul Rand

Shigeru Miyamoto and his team first designed the classic Super Mario Brothers levels on long paper scrolls. I find little hope of building a space as sublime and iconic as World 1-1 by bringing technology to bear too early--so don't open up the editor just yet. Start on paper. Try to give yourself (or beg your superiors for) enough time to think and to plan; it will pay off later.
Apologies for sounding like your gradeschool art teacher, but your most important tools are that piece of paper and your imagination. Especially in a production environment, some notes and a whiteboard or a few simple drawings can launch incredible ideas. A hundred different scenarios can be suggested and discarded before a single BSP brush snaps to the grid. Run with the ideas that intrigue you and don't worry too much about technical constraints just yet.
Get comfortable with thinking on the page; write down and sketch your internal dialogue. Don't trust that just because an idea is so awesome it means you'll remember it, or remember it in the same way. Buy a notebook or sketchbook if you don't already have one. As I point out in my article on character design, there's no need to get hung up drawing quality. Everybody can draw well enough to help develop layout ideas--simple lines and boxes will do just fine.
Brainstorm your approach to the level, specific sequences you might build around, hooks that make the experience of your level unique. Record them and then set them aside as you work. We'll cover the discipline of ideation in another update, but the important point is to not get married to the first ideas that crop up. You want to do enough thinking and doodling that you have the pick of the litter of many ideas in layout and encounters, not just being forced to execute on a small handful.
Try to complement this early planning stage with talking through your ideas with others. Kick them around with friends and coworkers whose sensibilities you trust. Try to get some feedback during all stages of development, even (especially) from people who you don't always agree with. George Lucasing it up with your own troop of yes-men is more comfortable but will ruin the work over time. Ideas get better--or at least the bad ones flushed out faster--once you try them out.

[We'll also leave out talking about research for the time being, but suffice it to say I am a strong proponent of research-driven approach to pre-production.]


2. Establish Scale

As you begin to rough in your level layout in the editor, one of your first priorities will be to establish scale. There's a reason why development textures for many games will have real-world comparison measurements all over them: you'll want constant markers and reference points to register the scale of your space.
With Darkest of Days there were several levels I sculpted the initial terrain for or also did a good amount of set-dressing, but did not script, and these are the levels I am most disappointed with because they are simply too large. The size of and therefore pacing of the levels are intrinsically distorted because I did not pay close enough attention to scale.
Terrain/outdoor spaces make it especially difficult to keep a grip on scale. You may think you can judge the scale of that hill you just raised, but in the abstract space of the editor it could be 20 feet or 200 feet.
For their part, indoor spaces also tend to require exacting consistency in calibration. Failure to do so will make for levels that will at best feel slightly "off" to the player, even if they can't articulate why.
Once you have created a terrain mesh or set laid brushes for your floorplan, immediately place objects in the world that you are intimately familiar with. Use the player character or as close to person-sized NPC as is available, cars and trucks, anything you know well. The closer they are to real-world objects the better, in order that you can fix them and your level in relation to real-world scale.
Here the first person perspective can be deceptive. your level can look normal sized while moving around in it alone because of no comparative cues--so be sure to place NPCs. In a pinch even a box, scaled to 6 foot high or so, will prove useful.
I recently did some work in UDK which was very interesting, because the tutorial/demo content is based off of Unreal Tournament 3. When a game is based on a traditional multiplayer deathmatch environment, double-jumps and all, objects and space are usually blown out a little to make room for the action.
A chainlink fence asset that I assumed to be about 8 feet tall turned out to be nearly 20 feet tall, skewed to the needs of UT3. Get to know your game's scale conversion between in-game units and the real world, so you can more accurately judge size relationships as you work.
Resist the temptation to leave obvious problems or faults in that "you will fix later." You will regret it. Small oversights become catastrophes with time. Once you're farther into building your level, recalibrating scale may become difficult or impossible without completely rebuilding.



3. Play and Pace

Play your level constantly, paying close attention to how the layout feels.
The map is not the territory, even in a virtual world. What you see or think you see while floating around godlike within your creation has little if anything to do with the experience of the player, which is all that matters. As soon as you've got anything to walk on, place scale references and start playing it.
Pace through your entire level's playable area/intended player path in real time. Do not cheat. However long your level should take to play through to completion, you should spend close to that amount of time pacing through every moment, every fight and puzzle, long before they exist to anyone else.
Go so far as to play out mock firefights, even with no enemies and nothing but a platform separating you from the endless void. Look at the outline of your level and consider the ramifications. Is this run-up too long, too short? Does the player have enough time to appreciate the clever visuals you have planned over to the left there--in fact, will it cross their sightline at all?
Changes that come from this initial read of the layout are critical. Over time, a level begins to harden and set like concrete. The accretion of set-dressing, scripting, sounds and AI behavior steadily freeze what at the start is fluid, so take advantage of it while you can.
The further into the process you get, the harder major changes become. As with planning, do not be afraid to make sweeping changes or start over. At this stage it costs a fraction of the time and energy it will to change later on.

When I build levels I pace through them obsessively, over and over; imagining the player's line of travel through the level as a kind of furrow I dig with my feet. As I walk through the level over and over, the furrow deepens and widens into a path, graded and accommodating.
When the player arrives the level will be "paved" in this way, suitable for him to travel and puzzle and battle in. Problems are anticipated and corrected by tirelessly pacing through the world at every stage of development, reducing the likelihood of playtesters discovering unknown corners, snagging on jagged edges unencountered by the designer. You built this world, you should know it better than anyone else.



4. Build Up The Canvas

This advice is also rooted in experience of making art. When painting it's very easy to get excited about a particular detail--an eye, an ear of a portrait--but then find yourself stymied, lost for how to finish the rest of the piece. You have a single excellent detail drawn but now you are worried because it doesn't seem to fit with the rest, you have no idea how to proceed--worse yet you've been captured by preciousness, wanting to preserver all the hard work you've just done, scared to ruin it.
Level designers reading this may recall similar experiences of building a room or a particular sequence to perfection, and then stare at the rest of the unfinished level with dread, unsure of how to continue.
To combat this, remember to "build up the canvas" equally. In painting, this means to develop the whole picture to roughly the same detail level in successive passes.
In level design, this means resisting the temptation to build, script, light, texture-align and set-dress a single room to finished quality and then move on. To be sure, some successive room-to-room building will occur but try not to. Your work will go more smoothly by building with successive passes, increasing the resolution of the entire design as evenly as possible. Not only will this help keep you from stalling out, but it increases consistency and makes practical sense in a production environment, allowing for more representative playtests sooner.
This principle is also applied to marker rendering techniques taught for product designers. Say your boss or your client suddenly wants the design now, not tomorrow or next week. By building the detail of the piece in successive passes, you can rest assured that if asked for early (or if it takes longer than expected) while it may not be overall to the finish level you wanted, it will be consistent and look equally "done" to the client.

Using this strategy the level always close to progressively higher states of "done". This will help you from getting caught setting a slower pace for building your level than you'll be able to complete on time.



5. Track Moment To Moment

Once you have the broader strokes, the pace and rhythm of the level right, you can step in and refine and develop the details. People remember and relate in terms of stories; refining the moment to moment narrative of your level is an excellent way to make it memorable.
By this I mean you should consider how a player would narrate, in simple terms, discrete events in your level. "I sniped the officer, crossed the bridge, set fire to the gas tank and saw some cool jets fly over, then got inside the mech and blew up a building."
A minute of gameplay is a year, three minutes of any one activity seems a lifetime. Breaking down your level in terms of these smaller sequences will identify problems and help suggest more discrete moments and encounters, avoiding tedium or repetition.
Clarify specific experiences within the level you want the player to have. where do they take cover? if they take time to look around, what details are they rewarded with? What might be found by carefully searching the scenery? Levels will often have a dialogue script, but what is the action script for the player like?

Take a look at your level and see if you can construct a basic narrative from the experience. Does the scenery blend together a bit too much? Ask your next playtester to briefly describe in basic terms what they did/what they saw, and see how easy it is for them. The more discrete moments or sequences they can recall, the better.


6. Factor In Testing

This is one of the most important aspects of level design, of game design as a whole: test early, test often.
Other people playtesting your level needs to happen almost as much as your own in-game appraisal of the work. The level is ultimately to surprise, delight, and challenge the player, not to hold a mirror to your shining glory and genius. You will have no understanding of how successful your level is--or how potentially rotten and recycled--until other people play it. Often the difference between good and great levels are just how much more thoroughly tested the latter are.
I feel the need to qualify this carefully given the rise of a certain perception of playtesters end up "dumbing down" great levels and mechanics, particularly for console games. There is a kernel of truth to this; occasionally games have been altered for the worse by improperly factored testing.
We must remember that the designer is not the player and the player is not the designer.
I could expand this key concept--a variation on what Warren Spector considers the "co-authorship" of games--into an entire article on its own, but the point is that we cannot let player feedback alone override good sense and instinct.
The player is not the designer. Playtesters are usually filled with a lot of worthwhile suggestions, but these should be considered with care. Watching a player play, monitoring their action directly says far more than they will tell you went wrong or right.
When you observe playtests you are looking for patterns, the larger and more varied the sample the better; unless hugely positive or hugely negative, no one single playtest should too strongly skew your perception of your level design.

But there again, the designer is not the player. There is no greater criteria for a level's quality than how well the player enjoys it. All that we do comes to nothing if it is not done with the player in mind. Developing good habits and remaining acutely aware of how your new level is taking shape can take a lot of the pain and frustration out of a long and sometimes maddeningly complex task.

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Tomorrow: the playtesting bonus round. Detailed description of my own methods, an argument for playtesting protocols, and why conducting disciplined playtests will make you a better designer. Quoth Aubrey: GET PUMPED.

Level Design Primer: Keep It Wide

I credit this rule to a friend of mine, Drew Risch. Mr. Risch was a professional architect for some time before going on to do level design on such titles as Planetside, designing several of the base layouts. Since then, Drew has recovered his sanity and traded in level design for effects work--but his design mentoring always proved invaluable.

This rule comes from the early days, where FPS players lept and bounded like strange, violent gazelles. Our younger readers may not know how different the early games were; for example, the running speed of the original Doom Guy in real terms is said to be about 60 mph. He could keep pace with a rocket fired parallel to him.
With so much play centered around mobility/maneuverability, a fun level was one that gave you enough space to work, but not so big as to be slack. You need room to circle-strafe, clearances to rocket-jump to. We may not be doing much of that in modern FPSes, but it's still important as ever to give the player room.

Boxed In

Recall the refrigerator box: the player is more unwieldy and blinkered than he thinks he is. Because of this, the level designer is called upon to build spaces around him that appear realistically scaled, but also tailored to mask the player's shortcomings. The simplest formulation of this design maxim? Keep It Wide.


This is to say, give the player room to maneuver/direct fire, and give enough space for clear visual navigation. A necessary corollary to this: the more players that play together in a space, the more room is necessary. Like all design rules, there are good reasons to violate this rule which we'll get to, but consider it good general practice.

Let us consider two scenarios--one from Valve's own Left 4 Dead campaign No Mercy, the other an excellent work in progress custom campaign, Highway to Hell.
Both campaigns begin in an apartment complex, but there are some crucial differences.

No Mercy: Bill is puzzled that the apartment's hallways are so generously sized, but knows he's got room to maneuver.

Highway to Hell: the survivors tend to see more of each other than zombies in some hallways. No place for a shotgun.

The setting and quality of set dressing are nearly identical, layouts very similar. One of the few small differences is that in Highway to Hell's apartment building, there are some extremely tight spaces for 4 players to fight through effectively. In L4D all players can freely clip through each other, which eliminates a lot of common related issues of this kind, but not all--friendly fire is still dealt. Which is exacerbated if players don't know the common practice of crouching if out in front.

No Mercy: Maybe a little oversized for the kind of mid-level apartment it would appear to be, but it gives room to play. No one joyfully shouts "this is so realistic!" when they're not having fun. (Outside of ArmA2 players, of course.)

Play through the beginning of No Mercy, paying attention to horizontal space. Most areas are built to accompany at least two abreast at any point--meaning if the two forward most players kneel, this is clearance enough for all four players to fire forward.
Not only does it make the game's stated emphasis on co-operative play viable, but it makes navigation easier as well--the more spatially restrictive an area is, often the harder it can be to clearly navigate. (In another update, I'll elaborate specifically on navigation considerations.)



The above shot is perhaps the diciest example from Highway to Hell. Most of the way through the map the survivors will wind their way through a meticulously recreated gas station.
The sense of place is very real, possibly to a fault: this communicating hallway is narrow and has a whopping six doors connected to it--to the front of the store, the back door, the break room, the restroom, and so on. While this is laid out realistically, suggesting it was all modeled on an actual gas station, it's also a death trap.
It's deceptively hard to move around in and direct fire, and if the Director throws down on the players through one of these connecting rooms--as it is wont to--the players might have a very hard time escaping, much less as a group.

I haven't had the pleasure of playing this map in actual co-operative play, only with bots, so I can't speak to whether the experience of it is panic inducing or annoying. The rub is that these two kinds of experiences live in very close proximity to each other.

Exceptions

This brings me to exceptions to the rule. Valve violates "Keep It Wide," that they otherwise strictly observe, in several key points throughout L4D. There is a storm drain sequence where it's obvious the players will only be able to advance in single file, a dangerous proposition in a world of zombies.
The above communicating hallway layout from Highway to Hell may also be an exception: despite being uncomfortably narrow to move and direct fire in, it is also small, and well connected, and veteran players should be alert enough in such a tight space. (Designing with the 360 version in mind would mean this area is simply out of the question, however.)

The more I think about it, the more I'm inclined to think it is an exception. Though I would note that the navigational issues (difficult to orient in such a nondescript corridor with so many doors) would be helped by introducing orienting details: restroom decal and possibly some chinsy art hanging on the opposite wall.

But the truth is, like every design decision made, you won't know until you get playtesters. If this area is consistently panicking players or making for some tense little shootouts, it's worth keeping, but if it's producing disproportionate casualties or an untoward difficulty spike, then it's worth revising.

Any design decision that violates best practices for level design in your game must be carefully considered. Is it breaking a rule in a fun, tension-inducing way, or is it doing it in a completely unfair, obnoxious way? You won't know without playtesting.

But rest assured that you'll address many aggravating issues with playtesting before they start if you remember "Keep It Wide."

[This was by no means intended to pick on the designer "Unlawful Combatant." Highway to Hell is absolutely professional quality work, and once its polished and completed it will rival or surpass a number of the original campaigns in the game; readers with L4D should check it out and see just how many of the previously mentioned Level Design Primer concepts they can spot (hint: basically all of them).]

Level Design Primer: The Sawtooth

Level Design Primer is an introduction to the high level concepts of first person shooter level layout and design.

As to credentials: for two years I built the majority of levels for the forthcoming single player FPS title Darkest of Days. Anything written here is backed by my own experience and observation from building and playtesting.

The sawtooth is such a universal staple of level design that once sensitized to, you will notice them everywhere. It is simple, effective, and (generally) foolproof.


The sawtooth stops the player from going backward. Simple as that. But as with other central design tenets of level design, simple can have far reaching connotations.
It takes innumerable shapes and forms: a broken staircase, a drop-down, a chute, a sheared cliff. Some are obvious, some are seamlessly integrated into the environment in a natural way, some are completely blind--like a ventilation duct that drops out from under you (groan).
Careful modulation of both the obviousness of sawteeth and their frequency are critical to the player's immersion. And the more "realistic" a game purports to be, the more carefully masked and generally less frequent they'll need to be to not be disruptive.

But why impede backward travel in a level? For single player games, there are a number of reasons: it makes life easier for the designer and the for the player in several ways.

The designer no longer has to worry about whatever the player is doing--getting lost, wondering where the party is, getting bored, and eventually quitting (which is the worst thing that can happen for a designer).
They can provide natural break points in the physical layout of the level to complement save points--which save in time, but not necessarily in space. Loading from a save point doesn't mean the player isn't still lost and might wander back to the start of the beginning of the level; a sawtooth means the designer knows for sure.
It's useful in tightly scripted "cinematic" action sequences where if the player otherwise may not know where to go or could veer off course too much and lose the immediacy of the engagement at hand.
Or, if the designer wishes to ambush or really rattle the player, certain kinds of sawtooth elements are useful to prevent the player from simply backing away from the encounter and cherry-picking the enemies from a safe distance.
The designer can also deactivate scripting or delete performance heavy entities or effects that they know for certain the player can no longer see.
This may just sound like its covering for lazy design, and while that does happen it also helps designers concentrate on crafting "the good stuff" rather than an increasing load of invisible-to-the-player housekeeping.

For the player it means a discrete point where, so long as he sees the sawtooth in advance, he knows he must be ready to progress.
For compulsive item and ammunition collecting players, approaching a clear sawtooth is a kindness; certain players hate not knowing if they'll be able to back and scrap up every last round of ammunition before moving forward.
And as previously mentioned, it ratchets physical progression through the level itself, effectively gating the play space into manageable chunks. This is helpful for designers, but aids navigation as well. In traditional "funhouse" like linear layouts, nobody wants to spend time wandering around the dead, empty portions of what they've passed through.

They're not just for single player layouts, either. For multiplayer levels whose flow tends to be circular and concentric, like a heart pumping its warring players into collision, sawtooth elements can still be useful in order to restrict two-way flow into more interesting one-way channels, say around a power-up.

To find examples of a sawtooth element, look no further than the best known FPS franchises with a linear single player or multiplayer component. A short list of recent titles would include Crysis, Call of Duty 4, Bioshock, Killzone 2, Left 4 Dead... you can find examples everywhere, once you look.


The critical view to sawteeth elements and their universal employment would be that they're a crutch that continues to prop up sloppy design and overly linear world design. So long as the kinds of things that make sawteeth such an obvious choice to use are present in level design, we'll continue to get fairly rote, linear "funhouse" type experiences.
But something as monumental as challenging concepts of linearity is outside the purview of this update--more on this sort of thing later.

Level Design Primer: S-Curve Variations

Level Design Primer is an introduction to the high level concepts of first person shooter level layout and design.
As to credentials: for two years I built the majority of levels for the forthcoming single player FPS title Darkest of Days. Anything written here is backed by my own experience and observation from building and playtesting.

Virtually all levels are about basic spatial progression, getting from the start to the finish alive. The job of a level designer is to make that progression as varied, interesting, and worthwhile as you can. Or as I like to think of the work: your job is giving the player an idea and make him think it was his. The better immersed he is in your world, the more he believes it to be his.

With this introductory primer, we'll be looking at some basics of path layout, high-level approaches that keep even a linear path interesting to most players if handled well.



1. The S-Curve
One of the single best guiding design principles for single player level design layout is the s-curve. The s-curve is central because it is the intersection of a variety of desirable qualities: ease of navigation, visual fidelity, interest and surprise. As a guiding high-level concept it will not make a level for you (nothing will), but it will enrich every level that it is incorporated into.

An example scene built in Far Cry 2 on a straight line. While this scene is fairly well composed visually, the path ahead is devoid of surprise. The player can see all three buildings on either side of the street plainly.

Starting out on a straight street or forest path with everything visible from the starting point makes traversing the space a chore; there are no surprises, it is merely ground to be covered.

Take the same path and introduce a slight s-curve. While the direction of travel is still clear, now portions of the path are occluded. Which makes for natural cover placement, enemy placement, or other points of interest. Now introduce vertical variation as well, and there is yet more occlusion as well as potential elements for vertical play. (This helps with the design maxim well understood by Valve that we'll get to later, which is that "players never look up.")

The same scene with a slight s-curve. The left portion of the street now "opens up" to the player, drawing his interest, while at the same time the middle right side of the street is occluded--to find out what's there, he's going to have to go down the street. Two sides of the bridge are now visible, making it more attractive as an endpoint as well. Where the player is standing is also slightly higher than the riverbank at the bridge, introducing more visual interest.

While only a brief sketch, we see how much more "opened up" the very slightly s-curved street layout makes the scene. This works hand in hand with "keeping it wide," another crucial level design maxim.

2. The Kinked Line
Take a soft s-curve and twist it around a bit more and you have what I call a kinked line. Like a garden hose held in hand, it restricts and slows down the flow of play in ways that can provide interesting variations, or opportunity for ambushes and the like. Hold a garden hose too tightly and the water stops completely, but held carefully and the flow can be manipulated. It helps creates more interest points in the path with reversals of direction, even if the overall direction of travel is still forward.

A benefit is that previous or later segments of the line can be made visible to the player, providing visual interest and incentive to continue, as well as helpful visual landmarks.
Kinked lines are quite regularly employed in linear games with real-world settings, since a kinked line or broken grid (see below) progression circumventing "normal" course of travel is accounted for.
The majority of the level paths in Left 4 Dead, for example, can be considered kinked line-style layouts.



3. The Stacked Line
Coil the player path even tighter than a kinked line and you get a stacked line. Like a ropey coil of intestines, the stacked line provides maximal travel time over the smallest area. It is useful for restricting player movement even further, for mood or practical reasons, or maximizing unexpected corners. With environmental density often at a premium, a stacked line can provide a "high value" area for production (though be warned that the player may not share your same estimation of "value.").

Anyone who has been to Disney World has seen stacked lines managed ingeniously--a large room might be used as the foyer to a ride. Yet instead of revealing that the entire room is filled with people waiting for the ride, partitions are introduced, blind corners, stacking the line in a coil which maximizes the room space without alerting any one segment of the line to the rest of it. Done poorly and the patron (or player) will realize what is being done and will be impatient, possibly indignant about the deception. Done well, and the subterfuge is invisible.

Stacked line sequences can be used as a "cool down," puzzle, or other severe restriction on the relative speed of player progression through the world, since the high frequency of 180 degree turns give them a maze-like quality. These must be employed rarely and with great care; perhaps one of the most notable examples of this layout style is the Nova Prospekt sequence in Half-Life 2. A number of levels from that game end up in this category, given that space is more of a premium and the largely corridor-based environments lent themselves well to this style.


4. Broken Grid
A classic level design form is what I call a broken grid, which is simply an interrupted grid with a snaking path or paths through it.

An area is devised along a grid--a city block, a warehouse interior, a colonnade--and then is "broken" so that the grid is only traversible in a modified path, though the grid itself is intelligible. This could be a deathmatch arena, with the breaks simply to provide cover and unique features, or more typically just a form for a single player linear path. The path is still variations on s-curves, but the player appears to be traveling through a grid (though not at all in a gride-like fashion). A broken grid is one of the easiest methods for creating an interesting or potentially multi-path area to progress.

A superlative example of broken grid-style layout on a larger scale would be Silent Hill 2. While the town of Silent Hill itself is shown on the map as a normal grid of streets, the player comes into contact with walls, fences, or gorges that break the grid in challenging ways. While the structure of the town and the basic path seems clear (and visible on the map), the complicating elements provide challenge where there would be little to none otherwise, and are dynamically marked on the map by the player's character.


All these examples may seem simple, but the strength of s-curves applied all throughout the many stages of level design work will eliminate many common problems relating to player confusion or slack time. When the world itself, devoid of items and enemies, is rich and appealing to navigate on its own, you are far less likely to have problems elsewhere.