Goal Hierarchies

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Structures of goals where the completion or non-competition of certain goals affects the possibility to complete other goals.

One of the typical design elements of games is goals. These provide players with motivation to perform various possible activities within the game system and to provide more details and sequences to these activities the goals can be organized so they build upon each other. Since this typically means that some goals can only be completed by first completing other goals, they often create Goal Hierarchies. These can let players have long-term and short-term goals that are interrelated or let players be provided with goals during gameplay as they progress through the Goal Hierarchies.

Examples

A good example of a Goal Hierarchies can be found in Zelda: A Link to the Past. At the start, Link is given the task of rescuing princess Zelda from the castle. After accomplishing this, Link is presented with a more elaborate quest of overcoming the evil wizard Agahnim. The subgoals of this task, such as freeing the seven maidens, are gradually revealed to the player during the gameplay and, near the end of the game, it is revealed that it is not Agahnim, but Ganon from the Dark World, that Link has to overcome.

Chess can be seen as a loosely defined implicit Goal Hierarchy. No pieces need to be captured from the opponent, nor any strategic locations occupied, to be able to checkmate the opponent's king. However, it does make the goal of checkmating easier, and nearly all players focus on achieving these subgoals before attempting to achieve the main goal.

The rough Goal Hierarchy in Pac-Man is as follows: eat the pills while avoiding the ghosts, get the power pill while avoiding the ghosts, chase the ghosts or eat the pills while under the influence of the power-pill, finish levels by taking all pills on each level, and finally get into the high score list.

Using the pattern

The most common way of constructing Goal Hierarchies is to create a structure where fulfilling the most accessible goals — leaf goals — leads to fulfilling other branch goals. Variations of this includes that completing leaf goals only makes possible or makes easier the completion of branch goals or that there are several mutually exclusive branch goals on the highest level. The goals by necessity need to be Predefined Goals if the Goal Hierarchies are supposed to be designed (rather than emergent or created by the players). Goal Hierarchies may also have different branches that split off from each other but rejoin later (e.g. succeeding in unlocking a door may allow the two goals of collecting parts of a code that together allow the hacking of a computer). More complex variants are possible but unusual, e.g. a cycle of inner goals that all can be started to be completed as soon as a dedicated leaf goal or the previous inner goal in the cycle have been completed. A goal that is used as a leaf goal becomes a Supporting Goal since it has a relation to a branch goal. Of course, Supporting Goals may also be branch goals to leaf goals, so Supporting Goals can both be modulated by Goal Hierarchies and modulate it. Note however that not all leaf goals need to be mandatory to fulfill for a branch goal to be fulfill; they can be Optional Goals which may make the branch goal easier (thereby becoming a stronger example of a Supporting Goal) or simply be something that can provide another type of branch goal for completionists. An obvious candidate for the innermost goal in a Goal Hierarchy is the Main Goal of a game. Tournaments can be seen as a specific type of Goal Hierarchies based upon making the results of individual game instances leaf goals of the branch goals of winning the Tournaments. Achievements, and especially Grind Achievements, is other ways of creating Goal Hierarchies by building upon already existing goals in a game and adding other goals outside the game (and thereby creating Meta Games). Support for Speedruns can be used in the same way. More implicitly, the possibility for Stimulated Planning in a game indicates that players can find their Goal Hierarchies. However, the existence of Goal Hierarchies in themselves promote Stimulated Planning, so the two patterns can instantiate each other depending on context.

Basically any goal can be a leaf goal in a Goal Hierarchy, but very common ones relate to Traverse, Capture, Collecting, defeating Enemies, or completing Levels or Minigames. Less common, but potentially important for players to experience narratives or that they can affect the game world are Companion Quests or those related to supporting or hindering the goals of Factions. Another less common example is the combination of Herd together with One-Way Travel, where each successful herding into a particular area of a game is a leaf goal of the branch goal of completing all herding goals. The most basic branch goal is the one that simply requires the fulfillment of all leaf goals associated with it. Selectable Set of Goals is a variation of this which allows a certain number of the leafs to be unfulfilled. Quests can support independent branch goals which can give players a sense of closure but also be used to partition large Goal Hierarchies in to smaller sections.

Goal Hierarchies and the specific goals they contain can be modulated in several ways. First, some of the goals in the hierarchies can be Excluding Goals to other goals in the hierarchies, making players have to choose which parts to traverse (consideration needs to be taken if the Excluding Goals can make it impossible to complete the innermost goals). Second, they may contain Unknown Goals that become reveal over time (perhaps as part of Narration Structures) as well as can be hinted at through Clues. Knowledge about the Goal Hierarchies, the goals, and even the Clues can be Strategic Knowledge, so that pattern can modulate the effects Goal Hierarchies have in a game. Third, the various goals in a hierarchy can change during gameplay through the use of Dynamic Goal Characteristics. Lastly, while any possibility to restore save points affect how players can explore and complete Goal Hierarchies, Save Points specifically be can used to signify to players that they have reached specific points in a Goal Hierarchy.

Quick Games can be difficult to combine with Goal Hierarchies (at least complex ones) since there simply may not be enough gameplay time to handle many goals and relations between them. Completing a Quick Game can however of course be a leaf goal in a Goal Hierarchy.

Narration Aspects

As other structures that may be hierarchically or sequentially structured, Narration Structures can provide the structure which is populated with goals to create a Goal Hierarchy.

Consequences

Goal Hierarchies often lead to Complex Gameplay since not only the structures suggest a more detailed relationship between goals in a game but can also make players need to think about these structures and how they wish to traverse them. Higher-Level Closures as Gameplay Progresses is also a common consequences of a presence of Goal Hierarchies in a game, at least as long as goals lower down in the hierarchies need to be completed before higher ones (or are the way higher ones can be completed). And, while Narration Structures can be the origins of Goal Hierarchies the opposite can be true in that Goal Hierarchies suggest or can work as the starting point for Narration Structures. One place where these consequences can merge is in games with Factions; here Goal Hierarchies involving the Factions is extra likely to create Higher-Level Closures as Gameplay Progresses that quite unavoidably also affects any narration.

Relations

Can Instantiate

Complex Gameplay, Higher-Level Closures as Gameplay Progresses, Narration Structures, Stimulated Planning

with Factions

Higher-Level Closures as Gameplay Progresses, Narration Structures

Can Modulate

Companion Quests, Enemies, Main Goals, Supporting Goals, Traverse

Can Be Instantiated By

Achievements, Capture, Collecting, Factions Grind Achievements, Levels, Minigames, Narration Structures, Predefined Goals, Quests, Speedruns, Stimulated Planning, Supporting Goals, Tournaments

Herd together with One-Way Travel

Can Be Modulated By

Clues, Dynamic Goal Characteristics, Excluding Goals, Optional Goals, Save Points, Selectable Set of Goals, Strategic Knowledge, Unknown Goals

Possible Closure Effects

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Potentially Conflicting With

Quick Games

History

An updated version of the pattern Hierarchies of Goals that was part of the original collection in the book Patterns in Game Design[1].

References

  1. Björk, S. & Holopainen, J. (2004) Patterns in Game Design. Charles River Media. ISBN1-58450-354-8.

Acknowledgements

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