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Abstract

This post originates from my external Blogger account KeepItVirtual, and is concerned with the optimal design and successful integration of emergent video game mechanics for systems that use Procedural Content Generation (PCG). The topics analyzed here within will provide descriptions and definitions of key approaches to video game design and procedural content generation, through research of specialized taxonomies and frameworks. A critical analysis will also attempt to address distinct correlations between emergent mechanisms in video games and PCG within complexity theory, as well as present logical conclusions and example designs.

Key Terms

Complex Systems, Design Patterns, Game Design, Game Mechanics, Emergence, Progression, Machinations, MDA Framework of Games Design, Procedural Content Generation (PCG).

Contents

1.     Introduction

1.1 The Structure of Gameplay

A game in its primordial form is defined by video game scholar Jesper Juul in his paper ‘The Open and the Closed: Games of Emergence and Progression’ as “a small number of rules that combine and yield large numbers of game variations, which the players then design strategies for dealing with” (Juul, 2002). What this refers to is the emergent style of play than can be exemplified in a game of Chess. In Chess, there is a relatively small set of simple rules that when combined, create a very deep and wide pattern of game play states. The pathway that a single game of chess can take between these states is known as the games trajectory through its probability space (Adams & Dormans, 2012). There are by far more trajectories in a game of chess than the original designer could have predicted. This is the primary understanding of emergence in games and is known to yield a high threshold of replayability. Emergence as a study refers to an aspect of Complexity Theory and Complex Systems which will be discussed further within this post.

Games of Emergence differ from Games of Progression however, which is a newer style of play, as first seen within adventure games, and is defined by Juul as a predefined set of actions to be experienced by the player in a sequence, such as a traditional lock and key mechanism. This method allows the designer much more control over the final play experience, but does not yield a high threshold of replayability, as the repeating of tasks can easily become monotonous. In terms of a game’s longevity, this suggests that designs of emergence are the more practical choice. However this concern of monotony can arise in Games of Emergence if a process is out of balance, reducing probabilty space and leading to a particular strategy being more efficient (Adams & Dormans, 2012). This imbalance can be countered using design patterns and frameworks to create mechanisms that feed internal elements back into play, or conclude the game entirely.

1.2 Gameplay Optimization

In game design theory, there exists a set of formalized guidelines that a designer can consider when developing ways of play within a system. This does not mean that the designer should feel in any way restricted, but rather empowered through an aided visualization of play states. These guidelines exist within two frameworks. A computational approach, as seen in Machinations Diagrams (Dormans, 2012), and a more philosophical standing, as seen in the MDA (Mechanics, Dynamics and Aesthetics) framework of video game design (Hunicke, LeBlanc, & Zubek, 2004). Machinations view game elements as resources within an internal economy, whereas the MDA approach considers all aspects of a game’s architecture as emotional inducers to the player. It is important to distinguish between play states as a collection of patterns that culminate a design vocabulary, and the design of such patterns with an optimal player experience in mind. This is what is considered at the core of each of the two frameworks.

1.3 Gameplay and Procedural Content Generation

Procedural Content Generation (PCG) is an area of study in computer science that is concerned with the automatic, or semi-automatic processes of generating content using pre-designed algorithms. Procedural algorithms are not random. They contain mathematical formulae that create a result. This means that the generation can be guided and create content that mimics manual development. In Chris Crawford’s book Chris Crawford on Games Design (Crawford, 2003), it is shown that algorithms can be thought of as data intensive or process intensive. The notion of data intensive programming is more focused on the storing and relocation of bytes within databases, but is performance heavy. Process intensive programming on the other hand is more concerned with formulae, and so more applicable to PCG. These both attribute heavily to the mechanics of progression and emergence (Adams & Dormans, p25, 2012). For games of progression, pre-arranged sequences of stored data are appropriate for the type’s structure. Emergence on the other hand is more associated with the processing of data, and computers are natural processors, able to create complex simulations in real time. Crawford believes all video games should capitalize on this more computationally optimal feature.

The applications of PCG prove heavily viable for video games, with examples seen as far back as Elite in 1984 (Holdstock, Fig. 1). Elite was a procedurally generated space flight, combat and trading simulator that included hundreds of algorithmically stored, procedural star system simulations. In the paper ‘Search-based Procedural Content Generation: A Taxonomy and Survey (Togelius, Yannakakis, Stanley, & Brown, 2011)’, it is noted that Elite displayed three very distinct benefits of using PCG in video game development.

As specified in the third, this technology allows designers to consider re-playability at a much grander scale than can be conceived with traditional designs, through the inclusion of near infinite content (Smith, 2014). In the contemporary video games industry, Sean Murray, the managing director of developer Hello Games has demonstrated a procedural video game universe in their product No Man’s Sky (Hello Games, In development 2014, Fig. 2). In his blog Murray notes that the procedures involved use a 64 bit system (2 to the power of 64) to deliver a ‘seed’ value within its range. This seed in turn is calculated against other values, such as the position of the player in Cartesian space. These calculations define logical parameters that specify attributes for star systems, planets, atmospheric scattering, ecologies, audio wavelengths and much more. This form of parameter based generation is defined as a Parameter Vector in the aforementioned Taxonomy developed by Togelius et al, and will be elaborated further within this post. In numerical terms Murray states that it would take 585 billion years to visit each planet if you could visit one every second (Murray, 2014).

It is procedural logic with pre-set formulae that allows for data to be generated and disposed of as players navigate the universe, allowing for a massive probability space, heavily in line with the understanding of emergence. In designing play for a system of this magnitude, Murray further explained during an interview at the PlayStation Experience event (December 2014, Fig. 3) that he intended to use a progressive mechanism as a means of creating structure within gameplay. His system increases the value of concrete resources, such as better performing equipment for the player to use, and abstract resources, such as threat, as the player travels towards the center of the procedural environment. The differences between concrete and abstract resources are distinguished further in this post. In correlation with the works of Deus Ex designer Harvey Smith, in his article ‘The Future of Games Design’ (Smith, 2001) on the need for game systems that focus on player expression, Murray further expresses how the game has been planned as an individual and personal journey. It is formed as a Massively Multiplayer Online Game (MMOG), with players freely exploring the universe in any manner that they see fit. He envisions the trajectory of play between players as “spokes on a wheel” around the center as players form together, although he notes events may not occur in this way, which is the true purpose of the design. Emergent play systems are, from a design perspective, a careful balance between player freedom and the control of the designer (Adams & Dormans, 2012).

In considering game design theory with PCG in mind, video game scholar Gillian Smith proposed a design framework for further developments in her paper ‘Understanding Procedural Content Generation: A Design-Centric Analysis of the Role of PCG in Games’ (Smith, 2014). Smith drew conclusions from the taxonomy of video game PCG proposed by Togelius et al. in their paper and combined them with the player-centric MDA Framework to produce a design focused vocabulary for video games with PCG that prioritises an optimal player experience, which will be discussed further in this paper. However, such existing frameworks, taxonomies and philosophies are yet to fully explore the direct implications and correlations of emergence for such content in specific regard to complexity theory, and so form the focus of this paper. Using applied research, this work will attempt to address the following questions.

2       How can we Accurately Approach Gameplay Design?

2.1 Game Design Theory as Mechanisms and Frameworks

A video game is often referred to as a state machine (Grünvogel, 2005) (Dormans, 2012).This is defined in the book ‘Game Mechanics: Advanced Game Design’ (Adams & Dormans, 2012) as a hypothetical machine that can exist in different states, with rules that govern how and when the machine should transition between these states. The term mechanics in a gameplay design context refers to theoretical structures used in directing the trajectory of a player’s interactivity through a game’s states, or probability space (Adams & Dormans, 2012).

In the PhD Thesis ‘Engineering Emergence: Applied Theory for Games Design’ by Joris Dormans, intricate combinations between several frameworks, including his own work on Machinations diagrams, are discussed extensively for creating such mechanisms. These frameworks constitute a design vocabulary that empowers designers in their work through an intrinsically focused view of gameplay. Dormans also notes however that “Due to the emergent nature of games it is often impossible to accurately predict the behavior of a game before it is implemented.” (Dormans, 2012).

2.2 Gameplay as a Vocabulary

One such framework that attempts to counter this ‘impossibility’ (of which also is a popular reference within game literature), was established in the paper ‘MDA: A Formal Approach to Game Design and Game Research’ (Hunicke, et al., 2004). MDA refers to Mechanics, Dynamics and Aesthetics. It is described as a formal lens from which to view a video game’s structure and was devised in an effort to unify the different professions found in game development, for the purposes of and optimized end user experience. It promotes a philosophy that each of these fields, such as art, technical staff and creative designers, all at some point have to consider the final experience of a game during development. These different visions combine as the project reaches conclusion, ultimately affecting the overall experience of gameplay, echoing complexity theory.

The approach views a video game as 3 combined components. These are the game rules, the game system, and the emotional experience induced upon players. A design perspective of these components equates to the Mechanics, Dynamics and Aesthetics of a game. The definitions as they appear in the paper are:

Mechanics: describes the particular components of the game, at the level of data representation and algorithms.

Dynamics: describes the run-time behavior of the mechanics acting on player inputs and each other’s outputs over time.

Aesthetics: describes the desirable emotional responses evoked in the player, when she interacts with the game system.

(Hunicke, et al., 2004)

The framework centres on ‘Aesthetics’ as the primary attribute, and expresses that the word gameplay is better replaced by a formal taxonomy to create a vocabulary that can focus more specifically on what experience the game actually delivers during play. The taxonomy as it appears in the paper is as follows:

1. Sensation -Game as sense-pleasure

2. Fantasy -Game as make-believe

3. Narrative -Game as drama

4. Challenge -Game as obstacle course

5. Fellowship- Game as social framework

6. Discovery -Game as uncharted territory

7. Expression -Game as self-discovery

8. Submission -Game as pastime

(Hunicke, et al., 2004)

‘Aesthetics’ are then used to dictate models of play, of which dictate the design of Mechanics and Dynamics for an emotive focused game. This means that the MDA framework focuses heavily on the resulting experience first, allowing the designer to choose which emotions are induced by the game. To clarify how MDA can be used, we can consider a dice roll, the Mechanics would be the roll of the dice to find a chance value, whereas the Dynamics could be how the result of that dice affects the number of movements a player may make in a board game. The design of this system could have stemmed from an intention to induce the Aesthetic of Sensation, such as risk or anticipation.

2.3 Dynamic Mechanics and Internal Economies

Using this framework, we can perceive mechanics and dynamics as a collective process that induces a predetermined emotion within a player. The framework paper shows how in board games that use two die for player progression, there is a predetermined probability in the chance value. A value of 7, as show in Fig. 4 (Hunicke, et al., 2004), has the highest chance of being rolled. This probability, by its nature, provides an average speed in which players can move around a game. Using this knowledge we can create dynamic mechanics that visualise game elements and player emotions as concrete or abstract data, forming an internal economy of resources. Resources in video games are defined in the book Game Mechanics: Advanced Game Design (Adams & Dormans, 2012) as any game element that can be defined numerically, and can be envisioned as an economy within a game. Resources can be further defined as:

As with any economy, we can consider the dynamics across values using defined economical functions, such as Sources, Drains, Pools, Traders and Converters. A Source in economics is any factor that can create resources, a Drain removes these resources, a Pool  is a place where resources gather, a Trader divides them between other factors, and a Converter changes their type to another (Adams & Dormans, 2012). This understanding of Dynamic Mechanics in an economical structure are what form the basis of a tool to design mechanisms of play known as Machinations (Dormans, 2012).

2.4 Machinations

A game’s internal economy, as with any economy, can be visualised with graphs, charts and diagrams. Machinations, as depicted in the PhD Thesis ‘Engineering Emergence: Applied Theory for Games Design’ (Dormans, 2012) are theoretical constructs by which a designer can visualise the play experience of a game within diagrams of that game’s internal economy. A prime example of this would be a Feedback Mechanism. A closed loop system that is designed to stabilize, or destabilize a certain factor in a system. In a game design context this would equate to creating balanced or unbalanced play through mechanisms that modify the abstract resources of advantage and disadvantage, and feeding them back into the game. In figure 5 (Hunicke, et al., 2004), we can see an example of a Negative Feedback mechanism that stabilises temperature through negatively altering its value. Figure 6 (Hunicke, et al., 2004) shows resource management game Monopoly, where there exists a positive feedback system in which monetary value is increased or decreased further as the game progresses. Figure 7 shows a similar feedback mechanism in a typical resource management video game, such as a real time strategy (RTS). This example uses Machinations to visualize an increase in monetary gain over time, as a player invests in additional workers.

Figure 8 shows a more intricate example of how a designer can use Machinations diagrams to visualize gameplay as a whole using the classic videogame Pac-Man (Namco, 1980) (Adams & Dormans, 2012). In the tool itself, these diagrams can run as simulations in in real time, with abstract resources such as threat increasing as more and more as ghosts enter play.

Double lined modules show player interactivity. Solid Arrows show rates in resource motion through a game and dotted arrows represent modifications to the state of these rates and as a consequence, the state of play. This is an extremely accurate approach for aiding the designer to visualize play experiences in video games and can be used in a variety of imaginative ways, such as using Pools and Arrows to simulate Progression or level transition or sources to simulate player’s entering a multiplayer game world.

3       How do we Integrate Gameplay Mechanics with PCG?

3.1 Mechanism Patterns

The concept of design patterns was first introduced in the book A Pattern Language (Alexander, et al., 1977) in an attempt to capture reoccurring patterns in architecture. This work formed the basis of many structural considerations, and of particular use for the structure of programs. In the book Design Patterns: Elements of Reusable Object-Oriented Software, it is discussed how patterns in logical script can be reused as templates for different scripts. Using this as a basis to understand logic in a video game, there are several conclusions that can be made regarding the transition of resources amongst game mechanic systems (See 2.4). In the book Game Mechanics: Advanced Game Design (Adams & Dormans, 2012), several patterns of play are shown within Machinations diagrams. These patterns are found to be reoccurring when simulating many different game mechanics with the tool. They can be pieced together to form more complex systems of gameplay. This also shows how play can be designed in tandem with a game script, or alongside programmers in a MDA (Hunicke, et al., 2004) focused approach (See 2.2). Such patterns are presented by Adams and Dormans and have been evaluated by them as to how they may play a role in gameplay functionality. Example patterns fall under categories such as Engines for a game mechanism, Friction between resources and Escalation across play states. The patterns come in many forms but a few core designs have been determined. Examples include (Adams & Dormans, 2012):

Engines

Engines in game design are any mechanism that can generate functionality within in a game, similar to an engine in a vehicle.

(You may notice a similar pattern in the dynamic engine above when viewing the example as shown in 2.4)

Friction

An example of multiplayer Friction in a game. This is known as Attrition, whereby attacks on an elements strength weaken its ability to perform.

Escalation

A game system that rises in a particular fashion. Learning or difficulty curves can be represented by an escalating pattern.

An example of multi-player Escalation. A positive feedback mechanism for 2 combatants that can upgrade an Abstract resource for offence. This is known as an Arms Race.

3.2 Game Design Vocabularies for PCG

Two very prominent papers are to be considered when designing play for PCG. These are titled ‘Search-based Procedural Content Generation: A Taxonomy and Survey (Togelius, Yannakakis, Stanley, & Brown, 2011)’ and ‘Understanding Procedural Content Generation: A Design-Centric Analysis of the Role of PCG in Games’ (Smith, 2014).

The first of these papers by Togelius et al., describe PCG, for both board and video games, as an Artificial Intelligence (AI) study, concerning the focus of procedural algorithms (see 1.3) to generate content by themselves. Several distinctions are presented in this paper for defining a vocabulary to be considered when creating PCG. The base definitions within the vocabulary are:

 (Togelius, et al., 2011)

The second of these papers, by Smith, draws from the taxonomy presented in the first, but through the philosophical lens of game experience as defined within the MDA framework (Hunicke, et al., 2004, See 2.2,). The purpose of the paper is to promote a similar vocabulary for game design and PCG that is more emotionally driven, by focusing on how PCG is aproached from each area within a game development pipeline. This is achieved in the paper through examining the concerns of the programmer, who is responsible for the generator, and the game designer who uses it. How the design of play is transmitted into the generator, is what is of most concern. This vocabulary falls under 4 key categories. These are:

 (Smith, 2014)

3.3 Order and Chaos

In recent paper by Joris Dormans ‘Making Design Patterns Work’ (Dormans, 2013). Dormans challenges the use of Taxonomies and Frameworks to define gameplay. He expresses that game literature and game development as an industry is heavily divided, and that developers are already able to form definitions in content themselves, and do not require theoretical ones by game scholars. He also states that a Taxonomy can be simplified to just categories of design patterns, and that to make them work we should not simulate initial play ‘ideas and concepts’ with patterns, but rather use them to find solutions to game design problems. He states in the paper:

In another quote from the same paper he states

Game design from concept to product is a hard process to achieve, and Dormans is suggesting that this is a possible future for design tools such as Machinations. What if we was to combine Dormans Machination patterns and PCG to form procedural patterns of play using algorithms? In his PhD Thesis ‘Engineering Emergence: Applied Theory for Games Design’ (Dormans, 2012) Dormans refers to Automated Design Tools and can be quoted:

He has developed a prototype of this feature known as Ludoscope.

4       Do Emergent Mechanics and PCG correlate as Complex Systems?

4.1 On Emergence

On considering Emergent design of mechanics, in personal correspondence with Ernest W, Adams, joint author with Dormans on the book ‘Game Mechanics: Advanced Game Design’ (Adams & Dormans, 2012) for the writing of this post, Adams can be quoted on Machinations:

The use of the word emergence predates its uses in the descriptions of gameplay types by Juul (Dormans, 2012). In the paper by Marcus Christen and Laura Rebecca Franklin ‘The Concept of Emergence in Complexity Science: Finding Coherence between Theory and Practice’ (Christen & Franklin, 2002), emergence is expressed as a central factor in complexity theory and the understanding of complex systems. These are studies of the relationships between individual parts of a system as they produce behavioral patterns within that system and are exemplified everywhere, such as the neurons within the brain or smaller networks within the internet (Bar-Yam, 2002) (Ladyman, et al., 2012).

4.2 Procedural Emergence

These parts in the context of PCG refer the algorithms used to create them. Procedural Emergence has been simulated in the studies of Cellula Automota, with a prime example in the work of John Conway in his Game of Life (Conway, 1970). That uses algorithms to express if cells in an image are black (alive in the his definition) or white (dead) based on the state of neibouring cells. 

What was most notable in examples created with the simulations, was that behavioural patterns emerge at different scales of the image when the simulation was ran. A procedural system is complex and so are mechanics within a game. They can be entwined and designed together using Feedback Loops as an example.

5       Conclusions

Complexity Theory and Emergence are known to be intrinsically linked to Game Theory. This is not Game Design Theory. It is the study of strategic decisions between rational thinking entities, through mathematical models of conflict and cooperation and is extensively linked to economics. Several Nobel Prizes have been presented to game theorists for advancements in the Sciences of Economics. Considering this research, there is a lot of thought that can be attributed to correlations between Internal Economies as detailed in Dormans work and real world economics. Is there room for an emergent, procedural economy in the non-virtual world?

It is worth noting that currently, the 'indie' market of the contemporary video games industry accounts for 54% of the current mobile gaming market (McKinsey, 2014) due to ease of scope and 3rd party engine availability. The inclusion of procedurally generated content is heavily viable within this domain as the techniques allow smaller development teams to create game play environments that can compete with larger studios. Mobile gaming is a domain within the industry that is growing at a rapid rate, primarily through the rise of interest in video games for mobile devices using 3rd party software engines (Helgason, 2014).

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