Understanding and Implementing Adaptive Difficulty Adjustment in Video Games

Understanding and Implementing Adaptive Difficulty Adjustment in Video Games

Tremblay Jonathan (LIARA,Canada), Bouchard Bruno (LIARA,Canada) and Bouzouane Abdenour (LIARA,Canada)
DOI: 10.4018/978-1-4666-1634-9.ch005
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This chapter begins with an introduction to different concepts evolving around the adaptive difficulty in video games (i.e. problematic definition, existing models of dynamic difficulty adjustment, evaluating the player’s experience, transposing the player’s skills into numerical values, using these numerical values as seeds for the difficulty level, etc.). Further on, this chapter covers the implementation of a novel adaptive model and the validation of such a model. This model uses a normal distribution system (ELO ranking) to determine the player’s skill level and then adapt the difficulty to their needs. In order to validate this model, 42 players play-tested two versions of the game, one with adaptive difficulty and one without any difficulty adaptation.
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The great video game companies such as Nintendo, Microsoft and Sony have succeeded in opening up the video game market to a wider audience of players (Pelland, 2009). This audience is composed of non-experienced and experienced players that share the same games. This reality has brought new challenges to game companies and game designers, such as making the game stimulating and interesting for this wider range of players. To reach all of them, the game has to provide the right amount of challenge for their skill level, as a game that is too hard or too easy is frustrating for them (Csikszentmihalyi, 1990). Also, one faculty of game, mainly used by serious games, is the capability of games to teach the player using game mechanics (the player’s actions) (Koster 2004). In this serious context, it is crucial that the game is able to reach a wider audience, for example in the classroom the game would be played by experienced players and neophytes alike. Therefore, it is important for the player’s experience that the challenge meets their expectations, as their enjoyment and learning results are closely related to the challenge. A classic approach to this conundrum is to let the player choose their difficulty level (easy, normal, hard, etc.) at the beginning of the game, without even trying it. Without any clear standard definition for difficulty, the player could easily choose the wrong level expecting the game to be something that it is not. This would lead the player to leave the game as they are experiencing frustration in the form of boredom and/or anxiety (Schell, 2008). Also, giving one unique level of difficulty is not really a proper solution, though it is a widespread one. Unique challenges are mostly interesting for a narrow range of players depending on their skill levels. Nevertheless, a well developed learning curve can bring many players, but the majority to the same point (Rolling & Adams, 2003).

To address this issue, some researchers and commercial video games such as Max Payne from Remedy Entertainment or Left 4 Dead one and two from Valve have built different models to dynamically adapt the difficulty of the game based on the player’s performance or intensity level. One of the main challenges regarding difficulty is the subjective factor that stems from the interaction between the player and the challenge. The perceived difficulty is also not a static property: it changes with time as the player learns the game skills (Goetschalckx, Missura et al., 2010). One of the major issues in this particular field is that the proposed approaches or games often do not offer any implementation explanations or guidelines for the dynamic difficulty model used. For example, the work of (Lindley & Sennersten, 2008) where they present an adaptive approach using gameplay schema that recognizes the player’s actions and based on them adapts the gameplay to the player’s preferences. In this particular example, the model is essentially theoretical and experienced in a non-realistic context. From this context it is nearly impossible to determine its actual effectiveness and bring to light the problems that had not been taken into account in the design. Nevertheless, experimentation and testing remain the best way to assure the robustness of a dynamic system.

Other works propose models that have been implemented and tested such as (Hunicke & Chapman. 2004), where they present a computational model using normalization distribution to evaluate the player’s skill level. A different approach proposed by (Chen. 2006) introduces a game design process leaving the player with the control of the difficulty of the game during gameplay. These types of work are essential for the comprehension and the elaboration of dynamic difficulty in games, for they give us an indication of how to implement and/or design their models. These works also provide discussion on their implementation and testing. They focus on how their models interact with the game but do not include deep explanations on the impact their model might have on the player.

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Table of Contents
Ashok Kumar, Jim Etheredge, Aaron Boudreaux
Ashok Kumar, Jim Etheredge, Aaron Boudreaux
Chapter 1
Jussi Laasonen, Jouni Smed
Moving in a formation is a basic group behaviour needed in computer games. This chapter presents different methods for co-ordinating formations in... Sample PDF
Co-ordinating Formations: A Comparison of Methods
Chapter 2
Thomas Hartley
Movement through a computer game environment is an essential requirement of non-player characters (NPCs) in today’s computer games. Local movement... Sample PDF
Adapting Pathfinding with Potential Energy
Chapter 3
Björn Knafla, Alex J. Champandard
Behavior trees (BTs) are increasingly deployed in the games industry for decision making and control of non-player characters (NPCs, also named... Sample PDF
Behavior Trees: Introduction and Memory-Compact Implementation
Chapter 4
Rob LeGrand, Timothy Roden, Ron K. Cytron
This chapter explores a new approach that may be used in game development to help human players and/or non-player characters make collective... Sample PDF
Nonmanipulable Collective Decision-Making for Games
Chapter 5
Tremblay Jonathan, Bouchard Bruno, Bouzouane Abdenour
This chapter begins with an introduction to different concepts evolving around the adaptive difficulty in video games (i.e. problematic definition... Sample PDF
Understanding and Implementing Adaptive Difficulty Adjustment in Video Games
Chapter 6
Luke Deshotels
This chapter will discuss several algorithms and techniques used in artificial intelligence that can be applied to StarCraft (Blizzard, 2009) and... Sample PDF
Application and Evaluation of Artificial Intelligence Algorithms for StarCraft
Chapter 7
Antonio M. Mora-García, Juan Julián Merelo-Guervós
A bot is an autonomous enemy which tries to beat the human player and/or some other bots in a game. This chapter describes the design... Sample PDF
Evolving Bots’ AI in Unreal™
Chapter 8
Ben Kenwright, Graham Morgan
This chapter introduces Linear Complementary Problem (LCP) Solvers as a method for implementing real-time physics for games. This chapter explains... Sample PDF
Practical Introduction to Rigid Body Linear Complementary Problem (LCP) Constraint Solvers
Chapter 9
Golam Ashraf, Ho Jie Hui, Kenny Lim, Esther Luar, Luo Lan
This chapter uses the Mechanics, Dynamics and Aesthetics (MDA) framework as a practical guide to incorporate the Rocket Jump mechanic in a... Sample PDF
Rocket Jump Mechanics for Side Scrolling Platform Games
Chapter 10
Benjamin Rodrigue
This chapter will describe several methods of detecting collision events within a 3D environment. It will also discuss some of the bounding volumes... Sample PDF
Collision Detection in Video Games
Chapter 11
William N. Bittle
GJK is a fast and elegant collision detection algorithm. Originally designed to determine the distance between two convex shapes, it has been... Sample PDF
Collision Detection Using the GJK Algorithm
Chapter 12
Sergei Gorlatch, Frank Glinka, Alexander Ploss, Dominik Meiländer
This chapter describes a novel, high-level approach to designing and executing online computer games. The approach is based on our Real-Time... Sample PDF
Designing Multiplayer Online Games Using the Real-Time Framework
Chapter 13
Aaron Boudreaux, Brandon Primeaux
The usage of software engineering principles in designing a game engine is discussed in this chapter using a simple tower defense game implemented... Sample PDF
Modular Game Engine Design
Chapter 14
Erik Hebisch, Ulrich Wechselberger
The study of video games involves many characteristics such as story, artwork and sound design. While it is possible to describe these qualities of... Sample PDF
A Gameplay Model for Understanding and Designing Games
Chapter 15
Chong-wei Xu, Daniel N. Xu
How does one design and implement a 2D game? Specifically, how does one teach students how to develop a game from an idea or a game story? A... Sample PDF
From a Game Story to a Real 2D Game
Chapter 16
Golam Ashraf, Ho Kok Wei Daniel, Kong Choong Yee, Nur Aiysha Plemping, Ou Guo Zheng, Teo Chee Kern
Vivace is an online musical tower defense game using the tree-of-life metaphor, created using the Unity3D game engine. The game integrates basic... Sample PDF
Music Tutor Using Tower Defense Strategy
Chapter 17
Damitha Sandaruwan, Nihal Kodikara, Chamath Keppitiyagama, Rexy Rosa, Kapila Dias, Ranjith Senadheera, Kanchana Manamperi
Games are used for other purposes than providing entertainment. This chapter is particularly interested in serious games, also known as simulators... Sample PDF
Low Cost Immersive VR Solutions for Serious Gaming
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