Non-Linearity

Non- Linearity

Non-linearity is another buzzword in the game industry, but like emergence, there is a lot of value to the concept. Non-linearity is what interesting gameplay is all about, and many game developers forget this in the heat of production. Non-linearity gives interactivity meaning, and without non-linearity, game developers might as well be working on movies instead. The more parts of your game that you can make non-linear, the better your game will be. Unfortunately, on the flip side, the more non-linearity your game has, the more time consuming and difficult it will be to develop.

In general, when someone says something is linear they mean that it follows a line. A line is a series of points connected in either two- or three-dimensional space, where one can find any point on that line using a specific equation, such as, in a 2D case, y = mx+ b. In layman s terms, this means that a line must be straight. If one considers any two points on that line, say A and B, there is only one way to navigate that line from A to B. There are no choices to be made; one simply must navigate all of the points between A and B. Outside the world of mathematics, we can consider reading a book to be a linear experience. If one is reading a 323-page book and if one does not skip pages or chapters, there is only one way to read the book: by starting on page 1 and reading all of the pages leading up to page 323.

Games , however, are non-linear works. In the game of chess, there are multiple ways to capture the opponent s king, to move from the game s predetermined starting state to its conclusion. Indeed, there are a vast number of different ways to be victorious in chess, and that variety is what keeps the game interesting. These choices make chess non-linear. Suppose the chessboard were one-dimensional instead of two, each player s pieces could only move in one direction, and each player had only one piece. This version of chess is a linear one, since there are no meaningful choices for players to make and the outcome of every game is completely predetermined. And, as a result, it would not be any fun to play.

Types of Non-Linearity

So when we say we want our games to be non-linear, we mean we want them to provide choices for players to make, different paths they can take to get from point A to point B, from the game s beginning to its end. We can mean this in a number of ways: in terms of the game s story, in terms of how players solve the game s challenges, in terms of the order in which players tackle the challenges, and in which challenges players choose to engage. All of these components can contribute to making a game non-linear, and the more non-linearity the developer creates, the more unique each player s experience can be. Furthermore, the different non-linear components can interact with each other to make the whole far greater than the sum of its parts.

• Storytelling: I discuss non-linear storytelling in more detail in Chapter 11, Storytelling. Of course, a non-linear story line is necessarily tied to non-linear gameplay, and no one would bother to try to make a story non-linear if the game itself offered players very little in the way of meaningful decisions. Storytelling is perhaps one of the most neglected parts of games in terms of non-linearity, with many developers allowing for non-linear gameplay while constraining their games to a completely linear story.

• Multiple Solutions: I discussed above how a well-designed game will enable players to come up with their own solutions to the challenges the game presents . Not every player will go about solving a situation in the same way, and, given that these alternate solutions are reasonable, almost any challenge must have multiple ways for players to overcome it. Having multiple solutions to the individual challenges within a game is a big part of non-linearity; it enables players to have multiple paths to get from point A (being presented with the challenge) and point B (solving the challenge).

• Order: Beyond being able to figure out the solutions to challenges in unique ways, players will appreciate the ability to pick the order in which they perform challenges. Many adventure games have made the mistake of being overly linear by allowing players access to only one puzzle at a given time. In order to even attempt a second puzzle, players must complete the first one. That is a linear way of thinking, which proves especially frustrating when players get stuck on a particular puzzle and, due to the game s linear nature, can do nothing else until that puzzle is solved . Giving players choices of different puzzles to solve allows them to put aside a troubling puzzle and go work on another one for a while. After completing the second puzzle, players may return to the first refreshed and revitalized, and thereby have a better chance of solving it.

• Selection: Another way of making a game non-linear is to allow players to pick and choose which challenges they want to overcome. Say that between point A and point B in a game there lies a series of three challenges, X, Y, and Z, which are non-order dependent, that is to say, players can do these challenges in any order they wish. What if, once players surmount challenge X, they do not have to go back and solve challenge Y or Z, they can simply move on to point B in the game, perhaps never returning to Y or Z? The same is true if players initially choose to tackle Y or Z instead of X. Any one of the choices will allow players to proceed. The advantage is that if players find challenge X to be insurmountable, they can try challenge Y or Z. This greatly decreases the chance of players becoming permanently stuck. It need not be the case that Y is easier than X; the mere fact that it is different may allow players a better chance of getting through it, depending on their strengths. Other players may find X to be easier than Y or Z, but giving players a choice of which challenges they take on allows them to exploit their own personal skills to get through the game. Of course, after completing challenge X, players may still have the option of going back and completing the Y and Z challenges, perhaps just for the fun of it or because overcoming those challenges somehow improves their chances down the line. Perhaps completing Y and Z gives their player character greater overall experience or riches. This type of non-linearity can also be used to add totally optional side-quests to the game. These challenges are not strictly required for players to get to the end of the game, though they may make it somewhat easier or merely provide an interesting diversion along the way. Whatever the case, these optional challenges provide an extra degree of non-linearity, further customizing players experiences.

Implementation

My first game, Odyssey: The Legend of Nemesis , is without doubt the most relentlessly non-linear game design I have ever done, and includes examples of all the types of non-linearity described above. Odyssey is an RPG and takes place on an archipelago that includes seven primary islands for players to explore. Though players are required to complete at least one quest on the first island before moving on to the rest of the game, there are two quests, each with multiple solutions from which players may choose. Indeed, clever players can skip the quests entirely if they figure out how to rob a particular townsperson. (In fact, this was an emergent behavior that I had not anticipated, but which fortunately made sense and did not derail the game significantly.) From there, players are able to move freely about the next five islands, picking which ones they want to explore and which they prefer to just pass through. Indeed, all that is required for players to reach the seventh island and the end-game is successful navigation of each island, killing the monsters that get in their way. Of course, killing those creatures is made significantly easier if players receive the rewards for completing the quests. But if players so choose, they can skip the entire middle of the game. Of course, few players have done this, preferring instead to explore the different quests and situations they encounter there. Nearly every one of these quests has multiple ways for players to solve it, with their actions having a direct impact on how each of the island s mini-stories resolves. Finally, the game itself has multiple endings for players to explore, endings that suit the different overall goals players may have: survival, revenge , or a sort of justice and harmony. Though the game had a very definite story, I am happy to say that I doubt very much that any two players ever experienced it in exactly the same way.

Odyssey is an extremely non-linear game, allowing the player to solve puzzles in whatever order he chooses and to select which quests he wants to go on. The game almost always provides more than one solution to any given puzzle.

Overall, my game The Suffering was significantly less non-linear than Odyssey , but still I applied many of the same non-linear storytelling techniques in order to give the game s story depth. The Suffering makes each player s experience unique through its morality system, which assesses how the game is being played and then determines the player character s past and changes how the characters in the present speak to him. As a horror game, the plot was kept somewhat vague on purpose, with players needing to fill in many of the blanks themselves . Furthermore, each player was likely to have a different subsection of the overall story, since much of the story is contained in optional side areas. Indeed, players who blaze through the game full speed ahead will miss a lot of the plot, while those who play normally will probably see about half of what there is to be found. This means there are many different ways to experience the story and players will have different impressions of it depending on how they play. Indeed, during development there was a lot of concern about players missing too much of the game by running through it quickly since there are relatively few bottlenecks to block progression. In the end, though, through gameplay testing and the feedback we received after the game shipped, we realized that almost all players will explore the game more than is required of them merely because they are interested in it. Similarly, players will fight creatures they don t strictly need to. It is important to remember that players want to play a game to have fun, and only the most masochistic will deliberately ruin their play experience. Thus you don t need to worry about the game s exploits quite as much as making sure the game is fun if played by cooperative players.

On the puzzle side of things, The Suffering is somewhat less successful in terms of non-linearity: many of the puzzles have multiple solutions, but an equal number do not. Though most of the objectives were planned to have multiple ways of completing them, we had several situations where one solution would involve an exciting payoff while the other did not. Our producers were concerned gamers would miss too much by choosing the alternate solution, and thus we ended up cutting some of the less exciting alternatives. This leads to an important rule of thumb: if you want to have multiple solutions or paths, they should all be equally compelling so players will not feel cheated at having picked the much less spectacular path . Another failed bit of non-linearity in The Suffering involved a particular level that was initially designed to be extremely non-linear. In this level, there were originally three separate paths leading to the level s end. Through our gameplay testing we learned that players were extremely confused by the three paths, with almost all players looping back to the beginning of the level and then being confused as to where they were. Admittedly this particular problem was due to poor level design, but this is a case where non-linearity ended up hurting the player s experience, and we ended up reworking the level flow in the final game.

Non-linearity is an extremely powerful tool to use in designing a game, and the above descriptions of the types of non-linearity a designer can employ may seem obvious to the reader. What is astonishing, then, is how many games fail to provide any substantial non-linearity for players, instead insisting that players play through the game on a single line from point A to point B. One reason for this is that creating all of these non-linear elements can be quite time consuming. Consider that between point A and B, we have the aforementioned challenges X, Y, and Z, but players only have to overcome one of these challenges in order to progress. Players can then continue playing through to the end of the game having never interacted with challenge Y or Z. As a non-linear game, that is the players prerogative. The problem arises when a cost accountant looks at the game and tries to figure out where the game s budget can be trimmed . Well, obviously, if Y and Z are not strictly necessary, why bother having them at all? Why spend a lot of money on the programming, art, and design necessary to get Y and Z working when there s a chance players will never see them? Unfortunately, accountants are often not in touch with the finer points of game design, and when you say, But non-linearity is what makes this game great! they are likely to dismiss you as unreasonable or difficult.

Working meaningful non-linearity into The Suffering proved quite challenging.

Non-linearity is also often hard to pull off from a design perspective, certainly harder than simple linearity. This may be another reason why so many designers shy away from it at the first opportunity. Designing numerous obstacles that are different enough to provide variety for players and apply roughly the same challenge is not an easy task. In the X, Y, and Z challenges example, if Z is significantly easier than X or Y, it is quite likely no one will ever bother with X or Y. In a way, a game with poorly designed choices for players is nearly as linear as a game without any choices at all. The non-linearity your game provides must be meaningful and useful to players or it is a waste. Designers who think too highly of their own design skills may also avoid non-linearity in their designs because they want players to experience every single element of the game they decide to include. Why spend a lot of time on portions of the game that not everyone will see? say these somewhat egotistical designers, missing the point entirely. If enough people play your game, some people will surely see what you have created, and each one of the players will have a somewhat different experience because of it. Just as a great novel will have multiple layers to its story and different meanings that different readers will take away, even more so a game should allow players to find their own way through the game-world and empower them to craft their own unique experience.

The Purpose of Non-Linearity

It is important to always remember that non-linearity is included in the game to provide players some meaningful authorship in the way they play the game. If they are forced to stay on a specific line to get from the beginning of the game to the end, the game will feel constrained. The challenges along that line may be brilliantly conceived, but if players have no choice but to take them on in order, one by one, the fun they provide will be greatly diminished.

Non-linearity is great for providing players with a reason to replay the game. Replaying a game where players have already overcome all of the challenges is not that much fun. In replaying a more non-linear game, however, players will be able to steer away from the challenges they succeeded at the last time they played and instead take on the game s other branches. However, it is important to note that replayability is not the main motivation for including non-linearity in your game designs. I have heard some game designers complain that replayability is unnecessary since so many players never manage to finish the games they start playing. So if they never finish, why add replayability? These designers do not realize that the true point of non-linearity is to grant players a sense of freedom in the game-world, to let players have a unique playing experience, to tell their own story. If players want to replay the game again, that is fine, but the primary goal of non-linearity is to surrender some degree of authorship to the players.

Furthermore, the contention that players seldom finish games and hence the games do not need to be non-linear is a self-fulfilling prophecy . The reason players fail to finish games is often because they become stuck at one particular juncture in the game. This may be a boss-monster that is too difficult, a puzzle that is too confounding, or merely failing to find the exit from a given area. If the game were more non-linear, however, players would have much less chance of getting stuck at any point in the game, since the variety of paths available would increase the likelihood that players unique talents would be sufficient for them to make it successfully through one of the paths.

At a Game Developers Conference talk entitled A Grand Unified Game Theory, Noah Falstein suggested that when non-linearity allows players to tackle a series of required challenges in whatever order they desire , completing one challenge should make the others easier for players to accomplish. In the case of a collection of puzzles, this can be done by providing players with a hint about the other puzzles once one is completed. In the case of a collection of battles of some sort, this can be done by providing players with additional weaponry with which to survive the other battles . Whatever the case may be, using this technique increases the chance that players will be able to overcome the challenges at hand and get on with the game.

A note of caution: all designers should understand that non-linearity is not about having players wander around the game-world aimlessly. If the game is non-linear to the point where players have no idea what they are supposed to try to accomplish or how they might go about it, the non-linearity may have gone too far. Often game designers talk up their in-development games by making statements like In our game-world, players can do anything they want; there are no restrictions. The game is completely non-linear! Such a game would likely be completely annoying as well. Of course, by the time these completely non-linear games have shipped, most of the non-linearity has been stripped out and players are left solving puzzles on a rail. Somewhere between on a rail games and total freedom lays an ideal middle ground, where players are left with a sense of freedom accompanied by a sense of guidance.