Defining Game Mechanics
Let’s start with a definition: game mechanics are methods invoked by agents, designed for interaction with the game state.
The different components of this definition require further explanation:
“Methods invoked by agents” defines this approach to game mechanics, as it formalizes the use of terminology taken from the object oriented programming paradigm (Weisfeld, 2000). In this appropriation of the terminology, object orientation provides a set of metaphors that describe the elements of systems and their interrelations. I do not want to imply that the analysis of the source code of a game will reveal that all game mechanics have been implemented as methods of classes or that object-oriented programming should be considered a default methodology for the actual production of computer games. Nor am I implying that the Object Oriented Framework should be extended to a formal analysis of all elements of the game. Object Orientation provides a clear, formal framework for the description of games and as such is a useful analytical tool. It is useful because it provides a formalistic approach to actions taken within information systems like games, which may lead to the application of modeling languages like UML to the description of game systems. The Object Oriented framework is also appropriate because it facilitates an analysis that does not require human players to understand in-game agency. In other words, by using an Object-Oriented approach, we can analyze game mechanics as available both to human and artificial agents.
Following object oriented programming terminology, a method is understood as the actions or behaviors available to a class (Weisfeld, 2000, p. 13). Methods are the mechanisms an object has for accessing data within another object. A game mechanic, then, is the action invoked by an agent to interact with the game world, as constrained by the game rules. In Gears of War, if the player wants to take cover, she has to press the A button in the controller. This will make the avatar seek cover in the closest environment object that can provide that cover. In that sense, a mechanic is limited by the rules that apply to the gameworld (the general physics simulations, for instance, whose objects are suitable for providing some kind of cover), and, on occasion, to rules that apply exclusively to that particular mechanic – for example, some mechanics can only be invoked in certain environments or gameplay contexts.
Following Järvinen (2008), the best way of understanding mechanics as methods is to formalize them as verbs, with other syntactical/structural elements, such as rules, having influence on how those verbs act in the game. For example, in Shadow of the Colossus we find the following mechanics: to climb, ride (the horse), stab, jump, shoot (arrows), whistle, grab, run (and variations like swim or dive). In Gears of War, a non-comprehensive list would be: cover, shoot, reload, throw (grenade), look (at a point of interest), use, give orders, switch weapons. All of these are methods for agency within the game world, actions the player can take within the space of possibility created by the rules.
This definition departs from the implicit anthropocentrism of previous approaches. Game mechanics can be invoked by any agent, be that human or part of the computer system. For instance, AI agents also have a number of methods available to interact with the gameworld. On occasion, those methods will be other than the ones made available to the human player, which can have consequences worth of analysis. This approach can be particularly interesting when trying to understand the effect of bots in MMORPGs, since bots are agents that optimize their interaction by focusing on a core set of mechanics. This design choice may lead to an imbalance in the game system, in terms of its dynamics or its economy. Another extension of this approach would draw a distinction between agents in a game with mechanics and agents without access to mechanics. For example, some bots do have access to mechanics while other game agents do not have access to mechanics and hence cannot interact with the game state. This line of research, however, is outside the scope of this article.
The second advantage is that it eases the mapping of mechanics to input devices, allowing for a great degree of granularity in the analysis of games. Applying the conceptual framework of Object Oriented programming determines that an agent invokes a mechanic in order to interact with the game. When it comes to players, input devices – from mouse and keyboard to the Wii Fit Board – mediate this process. In Gears of War, the cover mechanic is invoked by pressing the A button in the controller. In Orbital, the two mechanics are mapped to the two buttons of the Game Boy Advance device. Thanks to the formal precision of Object oriented terminology, it would be possible to use an abstract modeling language, like UML, to describe the interaction possibilities afforded to players, and how those are mapped to specific input device triggers.
For game analysis, this suggests the possibility of closely studying the relations between input device design, and player actions. It would allow, for instance, the study of how in some fighting games, one mechanic is not triggered by one button, but by a combination of input processes. Thus, it could be argued from a formal perspective that mastery in fighting games comes from the mapping (Norman, 2002, pp. 17, 75-77), of one mechanic with a set of input procedures, which leads to both psychological and physiological mappings – how the “body” of a player learns to forget about the remembering the illogical sequence of inputs, and maps one mechanic to one set of coordinated, not necessarily conscious moves.
Another interesting approach from this formal perspective is the possibility of describing mechanics that are triggered depending on the context of the player presence in the game world, what I define as “context mechanics”. In Gears of War, the cover mechanic depends not only on the specific input from the player, but also on the proximity of suitable objects to the player avatar. Contextual mechanics have also been used in Assassins’ Creed (Ubisoft Montreal, 2007) to expand the possible interactions of the player with the gameworld, without overtly complicating the layout of the controller device.
Contextual mechanics are analytical concepts that can be used to understand how players decode the information in a level – how a player perceives certain structures and how those structures are used to communicate intended uses or behaviors. Furthermore, contextual mechanics can also be used to analyze a game like Wario Ware, Inc., Mega Microgames! (Nintendo R&D1, 2003) that builds its design by mapping multiple mechanics (Järvinen, 2008, pp. 266-269) to one button, easing the players’ learning process and focusing on stress coping challenges (Rollings and Adams, 2007, pp. 287-288).
Implicit in this definition is an ontological difference between rules and mechanics. Game mechanics are concerned with the actual interaction with the game state, while rules provide the possibility space where that interaction is possible, regulating as well the transition between states. In this sense, rules are modeled after agency, while mechanics are modeled for agency.
In this object oriented framework, rules could be considered general or particular properties of the game system and its agents. All objects in games have properties. These properties are often either rules or determined by rules. These rules are evaluated by a game loop, an algorithm that relates the current state of the game and the properties of the objects with a number of conditions that consequently can modify the game state. For example, the winning condition, the losing condition and the effects of action in the player’s avatar health are calculated when running the game loop. This algorithm relates rules with mechanics, exemplifying the applicability of an ontological distinction between rules and mechanics.
For example, in Shadow of the Colossus players have a game mechanic called “climb”, but they are also determined by a property called “stamina”, which is the algorithmic translation of a rule: “players have x stamina units”. The climbing mechanic states that when invoked, stamina is lost at a certain ratio. A property/rule states that if stamina is below a certain threshold, climbing is not possible anymore. The game loop checks the game state; if the player invokes the climb mechanic, those functions that determine the consequences and boundaries of the players’ interaction are called, and the resulting changes in the game state are evaluated against the rules of the game. Then, the player will succeed or not in “climbing”, depending on their “stamina”.
The second part of the definition claims that game mechanics are methods “designed for interaction with the game state”. This implies that the task of game designers is to create mechanics that agents can use to interact with the game. These interactions modify the game state (Juul, 2005, 59-64). Game mechanics are often, but not necessarily, designed to overcome challenges, looking for specific transitions of the game state. Designers create the basic mechanics for the player correlating the central challenges of the game with the set of mechanics useful for overcoming them.
Challenges, like rules, are one of the contested areas in game research. Much has been written about what challenges are and how can they be analyzed, and it is not my intention to suggest a new interpretation of the term. In this article, I use challenge to refer to a situation in which the outcome desired by the player requires an effort to accomplish. For instance, every colossus in Shadow of the Colossus is a challenge, each of which is composed of a subset of challenges: the fifth colossus is a flying creature with weak spots in each wing and the tail. The challenge is to run from one weak spot to another without falling, since player movement is affected by the wind and the speed of the moving colossus. All these challenges are matched with a mechanic: by shooting arrows, the player calls the attention of the creature; by jumping and then grabbing to the hair of the creature, the player accesses a more or less stable surface where she can then run to the weak spots and stab them. All challenges in this example are mapped to particular game mechanics.
Even though this formal definition determines that games are structured as systems with mechanics, rules and challenges, understood as the essential grammar of computer games (and probably of all games), there is more to the act of playing a game than just interacting with mechanics constrained by rules. In the act of playing, players will appropriate agency within the game world and behave in unpredicted ways. One thing is what a designer previews, and another, very different one, is how players actually interact with the game world. The formal, analytical understanding of mechanics only allows us to design and predict courses of interaction, but not to determine how the game will always be played, or what the outcome of that experience will be.
Furthermore, it can happen that what was designed as a game mechanic is used in a non-gameplay related behavior: players of Shadow of the Colossus used the climbing mechanic to reach some of the farthest areas of the game world, which had no influence, or interest, for the central gameplay sequence and narrative of the game. Game mechanics are designed for gameplay, but they can be used for toyplay (Bateman and Boon, 2006). The only variation would be the level of abstraction: for a player who is playing the game, a mechanic serves a specific set of purposes, while a player that is playing with or within the game, a game mechanic loses its formal game design origin and becomes an instrument for agency.
For designers and theorists, game mechanics are discrete units that can be created, analyzed and put in relation to others. But for any agent in a game, the mechanics is everything that affords agency in the game world. Mechanics is thus tied to agency in the game system.
With this definition of game mechanics, I have intended to contribute to game studies by:
- Formalizing an ontological difference between rules and mechanics that can potentially lead to detailed game analysis, and
- Suggesting a mapping between game mechanics, input procedures, and player experience.
This very formal definition still leaves some questions unanswered, especially with regards to well-known terminology such as core mechanics. In the next section, I present some further implications of this definition for the analysis of games.