Evaluating Playability on Haptic User Interface for Mobile Gaming

Evaluating Playability on Haptic User Interface for Mobile Gaming 2 3 4 Chui Yin Wong \ Kimberly Chu , Chee Weng Khong and Tek Yong Lim

123 Interface Design Department, Faculty of Creative Multimedia, 4Faculty of Information Technology, Multimedia University, Cybeljaya, Malaysia { cywongl , kimberly. chu2 , cwkhong3, tylim4}@mmu. edu.my

Abslracl-There have been escalating research interests on areas relating to haptic modality in recent years, especially towards mobile devices. However, there seems to be limited studies in determining the relation between haptic user interfaces and its influence on the playability of mobile games. This paper aims to measure playability of mobile games by comparing two different types of haptic interfaces, namely hard and soft keypad, for mobile gaming. The results show that the participants (N=12) scored highest in using a soft keypad (mean = 591.92, SD = 322.57) as compared to playing games using a hard keypad (mean

=

471, SD = 359.29). However, this paper highlights that

the majority of users prefer using the hard keypad method in virtue of greater player experience with regards to game play.

Keywords- haptics; playability, mobile game, soft and hard key

I.

user interface; evaluation;

INTRODUCTION

Mobile phones are fast becoming ubiquitous in determining the styles and trends of everyday communication for human kind in this modem world. W ith enhanced hardware and software in mobile phones, and increasing network enhancements, it is no doubt that mobile phones provide a viable platform for hosting personal games. M obile games are one of the most proliferating industries with growing demands from the mobile users. As mobile phones evolve, m ore advanced functions and user interfaces are added to provide greater user experience. These additional features include touch screen, the ability to detect device orientation and motion via accelerometers, and also the ability to measure the strength and direction of the magnetic field by using magnetometers. PDAs, smart phones, Android phones, and pocket PCs with touch screens are fast gaining popularity among users the world over. Nowadays, with technology advancement, more mobile device manufacturers are adopting touch screen or haptic technology due to its decreasing price and mass manufacture. For instance, [I] highlighted that the emergence of touch screen is changing the landscape of gaming industry. The success ofNintendo DS, as one good example, had shown great ideas on the gaming possibilities. As a consequence, touch screen-based games are perfect examples of how haptic technology can advance the gaming industry and benefit from its popularity. The aim of this paper is to evaluate playability on two different types of haptic user interfaces for mobile gaming. In this paper, Section 2 depicts the discussion on haptic modality

978-1-4244-6716-7i10/$26.00molO IEEE

on mobile user interfaces; whilst Section 3 discusses the challenges of playability for mobile gaming. Section 4 examines a user evaluation study for measuring playability by applying two different types of haptic user interfaces for mobile gaming; followed by a closing remark and recommendations for future work in Section 5. II.

HAPTIC MODALITY ON MOBILE PHONES

The use of haptic modality such as touch screen has recently received popularity among the mobile phone users as it is a relatively fresh interface from the usual hard keys. The characteristics of touch screen-based mobile phones are that they usually have fewer push buttons and the users interact with the interfaces by touch. With the development of touch screen-based phones, like Motorola A 1 200, HTC Diamond, Sony Ericson w960i, Samsung Ultra Smart F520, Apple iPhone, Android T-Gl, Nokia XpressMusic 5800 and Blackberry Storm, new forms of user interaction technique have appeared through the use of fingers or a stylus pen. These types of mobile devices utilize gesture as the means for data input to allow much easier user interaction; for instance, flicking the fingers on the touch screen for browsing through the web pages, zooming options for photo viewing and many others features. In addition, majority of the touch screen devices have two kinds of gesture input that is, dragging (users touch tap on the screen surface while moving slowly across the screen) and pressing (users press harder on a device surface). The successful launch of Apple iPhone in June 2007 has revealed greater opportunities for mobile device manufacturers to produce various mobile phones m odels using haptic modality and multi-touch display. This opportunity also came about as capacitive touch technology was made widely available for third-party development. Multi-touch with a gesture option as a possible input method for mobile user interface. For example, it features flicking, tapping, pinching and stretching. With only one physical button, most user interactions are performed via haptic interactions on the Apple iPhone. With reduced number of physical button in mobile devices, the frame of a mobile display can fit onto a larger display hence providing the opportunity for designers and engineers to enhance the visual feedback which in tum enhances the pl ayer experience during interaction and gameplay.

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By adding touch screen that is coupled with a higher mobile screen display resolution and by augmenting its processing

•

Immersion: The capacity of the game contents to be believable,

such that the player becomes directly

power, it will enhance the enjoy-ability for existing gamers,

involved

and also attract potential new gamers. For instance, hardcore

Conscious,

gamers will be able to reach greater heights in terms of

Dexterity, and Socio-cultural Proximity.)

playability with an enhanced credible gaming platform. On the other hand, the ease-of-use of touch screen will also attract

•

•

set

of

world.

(Properties:

Absorption,

game

Realism,

characteristics

that

Curiosity,

Self-improvement,

and

Emotion: The player's involuntary impulse in response to the stimulus of the game the game that induces

increase in user satisfaction for the overall game

feelings or a chain reaction of automatic behaviors.

experience with advanced haptic interface as compared to

(Properties: Reaction, Conduct, and Sensory Appeal.)

simple on-off vibration or merely audio feedback. In addition, •

Socialization: The set of game attributes, elements and resources that promote the social dimension of the

that users have little preference in using buttons over gestures.

game experience in a group scenario. (Properties:

The study indicated that touch screen-based devices provide

Social

much more freedom to the users in terms of control as

Perception,

Group

Awareness,

Personal

Implication, Sharing, Communication and Interaction.)

compared to buttons-based mobile phones. In a nutshell, the players' attention is enhanced while interacting with touch

game

Diversity.)

industry.

a mobile first person shooter (FPS) game. The result showed

The

Encouragement,

create new opportunities to tap into this lucrative gaming

[3] presented a study of using pen gestures instead of buttons in

virtual

Awareness,

undertaking them until they are completed. (Properties:

mobile games. Given this notion, touch-screen-based mobiles

1 5 - 1 7%

Motivation:

the

prompt a player to realize specific actions and continue

potential casual gamers to indulge in touch screen-based

A user preference study [2] on mobile games also showed a

in

Nonetheless,

current

mobile

phones

lack

usability

as

phone surface, thus increasing playability and the players'

compared to handheld consoles, such as the Nintendo Wii or

experience.

the Sony PSP [6]. With such a lucrative business and potential huge market for gaming industry, there are still a lot of rooms

CHALLENGES OF PLA YABILITY FOR MOBILE GA MING

III.

for development if mobile phones are going to cater for mobile gaming. [7] also argued that the current mobile devices did not

Playability is depicted as 'the instantiation 0/ the general concept of usability ... determin.?d by ... understanding and controlling game play' [4]. The concept of playability is

appear as a feasible means for game play as they entail too

associated

communication purposes, the level of playability for mobile

with

fun,

flow,

fulfillment,

player

experience,

satisfaction, engagement and pleasure. In a playability study on video game, [5] argued that playability is not limited to the degree of 'fun' or 'entertainment' experienced when playing a game. Instead, playability is defined as

'a set o/properties that describe the Player Experience using a specific game system whose main objective is to provide enjoyment and entertainment, by being credible and satisfying, when the player plays alone or in company'. To

characterize

experience with

7

player

experience,

[5]

relates

player

attributes that affect playability, which are

satisfaction, leamability, effectiveness, immersion, motivation, emotion, and socialization. Each of the playability attribute is described

in

relation

to

their

distinct

characteristics

and

properties: •

Fun, Disappointment, Attractiveness.)

•

buttons. Even though mobile phones are generally designed for garners is somewhat awkward, static and uninteresting. With limited keypad space and miniaturized input and output modalities, this eventually gives rise to a rather limited game input control [8,

Leamability:

Player's

capacity

to

9, 1 0 ,

II]. Ultimately, this limits the

gratifYing user experience one would expect from gaming altogether. The consistent and prolonged use of the mobile phone hard keypad will undoubtedly cause repetitive strain injuries (RSI) on the wrists, fingers and other upper body parts. The issues of RSI, Blackberry Thumb and tenosynovitis are common health hazards faced by users who spend long durations on their mobile phones while playing games [12]. Undoubtedly, such symptoms will deteriorate the enjoyment, fun and affect the player's experience. IV.

Satisfaction: Gratification or pleasure derived from playing a game or from some aspects of it. (Properties:

•

much attentiveness on controlling the game with cramped

USER EVALUATION STUD Y

We conducted an initial user evaluation study to measure the playability of haptic user interfaces for a mobile game. In

understand

and

this pilot study, we compared two different types of input

master the game's system and mechanics (objectives,

methods for haptic modality on mobile phones. They are soft

how to interact with a game).

keypad (for a touch screen-based mobile phone) and hard

(Properties:

Game

Knowledge, Skill, Difficulty, Frustration, Speed, and

keypad.

Discovery.)

triggered by the soft keys for its functionality, which is a

Effectiveness: Time and resources necessary to offer players a fun and entertaining experience whilst they achieve the game's various objectives and reach the final goal. (Properties: Completion, and Structuring.)

Touch

screen-based

mobile

device

is

primarily

simulated button or keyboard that is displayed on a touch screen [13]. A soft key is also defined as a button flexibly programmable to invoke a number of functions rather than being associated with a singled fixed function or a fixed set of functions [14]. Hence, soft keys are usually located adjacent to

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a screen or a readout that displays the function selected when the key is pressed. On contrary, hard key refers to a hard­ coded key such as a number key pad or the Send/End key of a mobi le phone. The apparatus used for the user testing was a Nokia N82, configured as a hard keypad device, and a Nokia Xpress Music 5 800 with its touch screen interface configured as a soft keypad (Figure I ) .

F igure 3 .

B.

F i gure 1 .

A.

A No ki a N82 used fo r hard keypad ( left ) , and No kia Xpress M usic 5 800 fo r soft keypad o r touch screen (right).

A Mobile Game - 'Capture'

A classic game called ' Capture' was selected due to the adaptive screen resolution available for both soft keypad (touch screen) and hard keypad on mobile phones. The concept of the ' Capture' game is to encourage the players to fill the block on the mobile screen by capturing the flies flying around, whilst avoiding being 'killed' . Each player is given 3 ' lives' at the first level until s/he manages to fill the block. Once the block is filled, the player is promoted to the next level up. The higher the levcl, the more challenges the player wi ll encounter to capture the flies. Figure 2 and 3 shows how the ' Capture' game was played on both mobile phones - hard keypad on Nokia N82, and touch screen on Nokia Xpress Music 5 800 .

F igure 2.

The 'Capture' game play o n No ki a N 82 , a mo bile phone w ith a hard ke ypad. ).

Participants

During this user trial, 1 2 interface design undergraduate students (7 male, 5 female) were selected to participate in this study. Their age range is from 1 9-2 I years old (mean=20 , SD=0 .95) . In general, al l the 1 2 students own a mobile phone with hard keypad, and they do not have any prior knowledge on touch screen-based mobile phone. In addition, they have been using mobile phones between I to 8 years (mean=4.55 , SD=2.70) . All 1 2 participants except one have been playing games on the mobile phones. C.

Procedure

We conducted the user trial in three sessions, namely pre­ test, testing and post-test. Firstly, the participants were informed to fill in a pre-test questionnaire before they engaged with the game play. The pre-test questionnaire is to determine the demographic profile of the participants which includes age, gender, mobile phone usage, and mobile game experience. To find out their general opinions on game, the participants were prompted further when and how they started engaging in their previous game experience, and their overall ideas on enjoyment and fun on the game play. After the first test session, the participants were required to engage with the ' Capture' game on both mobile phones. Either soft key (touch screen) or hard keypad mobile phone was selected randomly to avoid selection bias. The 1 2 parti cipants were requested to familiarize with the game for 5- I 0 minutes before we started recording the game play session. Figure 4 shows a female participant interacting with the ' Capture' game on the mobile phone.

The 'Capture' game play on No kia Xpress Music 5 800, a mo bile phone w ith soft keypad (to uch screen ).

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Figure 4.

A female participant is testing the 'Capture' g ame play on Nokia N 82, a mobile phone with a h ard keypad.

We adopted the 7 play ability attributes [5] to measure play er experience in comparison with respective haptic user interface to play the ' Capture' mobile game. During the game play session, a facilitator observed and recorded whether the participants completed their task, input errors, numbers of thumbs used during the interaction, highest game scores, facial expression, and think aloud comments. It is noticeable that some participants wrongly pressed some buttons, and the flow of the game halted due to errors and interruptions. The facilitator would observe and prompt the part icipants how they would deal with the situation . If the participant felt clueless and confu sed, the facilitator would assist and resume the game in order for the participant to resume their focus back on the game. Upon completion, the participants were debriefed and guided with a post-test questionnaire. During the post-test, participants were asked about their preferences between the tw o input methods and the player experience against the playability attributes checklist. Each participant was briefed about the meaning of the playability attributes. There were no restrictions for them to choose the number of play ability attributes that associ ate with the game play in the playability checklist. In between sessions, participants were given a short break in order for them to fully maximize their experience of the game play rather than feeling disturbed with the questions which might affect their play ing experience. D.

Results and Discussions

The results in Table I shows that the average score of playing the ' Capture' game on soft keypad is higher (mean= 59 1 .92 , S D=322 . 5 7) than the hard keypad (mean=47 1 , S D=3 59.29) . Eight out of twelve participants scored higher on soft keypad (touch screen s) as opposed to hard keypad during the game play . In terms of the game score for soft keypad (touch screen) , the highest score is 1 099 (N3) and the lowest is 32 (NI0) . On the other hand, the highest game score for hard keypad is 1336 (N6) and the lowest score is 64 (NIO) . During the debriefing session, the participants were prompted their keypad preferen ce as input method for game play , 10 out of the 12 participants responded they preferred hard keypad for playing games. TABLE I.

RESULT S SIIOWI NG TilE IIIGIIEST SCORE OF TIIEGAME rLAY ON BOTII IIARD AN D SOFT KEyrAD (TOUCII SCREEN). Keypad

o.

ender

. ighest Score using SK

i :ighest

Preferences

Score

as Input

using i iK

I .rror !etection SK or

Method for

liKII

I 'ame PiaV

NI

Ma le

306

*340

N2

Ma le

*751

608

N3

Fema le

* 1 099

N4

Fema le

*547

N5

Ma le

*1092

909

HK

N6

Fema l e

724

*1336

HK

N7

Male

*365

224

HK

N8

Fema le

266

*413

HK

SK

0

HK

3 (H K)

541

SK

2 (H K )

543

HK

0 0 I

(H K) 0

2 (H K)

N9

Male

*747

2 87

HK

0

NIO

Female

32

*64

HK

2

Nl I

Male

*675

2 83

HK

3

NI2

Male

*499

1 04

HK

0

Male- 7; Mean-59 1 .92 Femal�5 Nole: * means hIgher score

Mean�47 1

SK: Soft Keypad (Touch Screen) HK: Hard Keypad

It is interesting to learn that those who scored higher on the soft keypad are in contrarily with their preference choice on hard keypad (i.e. N2 , N4 , N5, N7, N9 , N I l and N I 2) . Perhaps all of the 12 participants, who are currently hard keypad mobile users, was the fi rst time experiencing the mobile game play on a soft keypad (touch screen) . They also commented they preferred hard keypad over soft keypad due to the tactility of the sensation on pressing the hard keypad as opposed to soft keypad. For instance, N Il expressed he liked hard keypad because it was easier to navigate on the controls and move around the keypad. He also expressed the sensation of a tactile reference was important. In terms of hand-device interaction, 6 out of 12 participants used one thumb to navigate the game (N I , N3 , N6 , N8 , N IO and N I l) . On the other hand, another 6 used both thumbs during game play and interaction (N2 , N4 , N5, N7, N9 and N I2) . It is interesting to learn that those who scored higher using the soft keypad (touch screen) usually used both thumbs to navigate through the game controls. It is observed that those who scored higher with the hard keypad generally used one thumb to interact with the game. During the debriefing session, the participants expressed their opinions about mobile games. Some mentioned that they play games on their mobile phones while waiting for a friend, before sl eeping, or whenever they feel bored. They highlighted that reaching a higher score, breaking a new record and winn ing a game is the most fun. It provides them the highest feeling of achievement in their game play experience. In terms of the mobile usage, the most frequent activities reported are making calls, sending text messages (SMS) , play ing games and li stening to music on the mobile phones. Figure 5 shows the parti cipants' preference towards the playabi lity attributes in a word cl oud fashion illustrating the frequency of responses from the participants . For in stance, the relative frequency of ' satisfaction' is II counts whilst the second highest frequency shows 6 counts for ' motivation' . This is followed by 'immersion' (2) , 'emotion' (4) and 'Iearnability' ( I ) . E ffectiveness and soci alization attributes were not sel ected by the respondents could be due to the context of the 'Capture' game. In such a user evaluation study , the respondent was conducted in an in dividual section , where ranking and higher score are not taken into considerati on. The user testing was rather to evaluate which haptic user interface gives more enj oyment to the player. If the game play is a multi -player game , it will encourage the players to social ize with other play ers while attempting to achieve higher score, or compete with other player. During the post-test session , it was found that the playability attribute most important to the participants is

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sati sfaction, followed by motivation. E motion and immersion were noted as being very closely rated while learnability was lowly considered by the participants during the study. The properties of satisfaction includes fun (achieving game obj ectives and getting high scores) , disappointment (making less errors during game play , less cramped screen management, easy to learn) and attractiveness (aesthetics and content design).

motivation

emotion

satisfaction immersion

Figure 5.

Degree of playabi l i ty with its selected attributes considercd by players during game play.

V.

test is better conducted using multi-method approaches to cross-validate the test result. In future, we plan to examine the different variables such as the button lay out, size, and shapes in determining the player experience. In addition to this, our future plan also intends to study the consequences and feasibility of allowing players to re-size the soft keypads through the game preferences in relation to the game genre. For example, customizing one soft button for a simple shooting game rather than having 5 navigational buttons activated on the device. Studies can be conducted to relate the size of gaming key s against game score, anthropometric data, economics of play ability , screen management, and practicality. In terms of player experience, play ers highlighted that having high score or breaking records as being the most "fun" part for them during game play. There is also the possibility of studying the effects of cross-input mechanisms instead of purely keypads and its soft derivation. The combined use of a mobile device's microphone, camera, accelerometer, magnetometer, etc. provide further research opportunities in study ing its effects towards the gaming experience as these functions are becoming Ubiquitous with the production of current mobile technologies.

CONCLU SION

All haptic user interfaces and its input mechanisms have their intrinsic advantages and disadvantages. Soft key s may fare well in some aspects over hard keys, and vice versa. Based on the analy sis of results, it is observed that a greater percentage of mobile game play ers tend to have a higher score via the touch screen interface, and barely made errors during game play. On the other hand, the results also highlights a possibil ity that the subjects are comfortable with using hard keypad on the mobile phone as indicated from their opinions during the interview. Nearly 84% of the subj ects mentioned that they prefer using hard key s while the others prefer the touch screen. The non-phy sical attributes of the touch screen with its capacitive surface, its nature of use, and its supporting software development somehow provided additional flexibility in terms of the design of the overall interface, screen size, spatial considerations (screen management) and the display ed button sizes. On the other hand, hard key s seem to provide little flexibility in customizing the size of the keypad buttons as its manufacture and design are standardized, unless by changing mobile phone model s. With touch screens, a larger screen size can be achieved as there is no phy sical need to accommodate screen space for hard keypad buttons. The sizes of buttons will automatically be bigger, thus providing a perceived larger space to press and play around with. Nonetheless, players can opt to use a sty lus to play on touch screens as some touch screen phones are provided with one. Since the percentage of play ers achieved higher scores by using the soft key (touch screen) , this pilot study summarizes that the soft key s on touch screen provide better player experience during game play. Although this pilot study only employed 12 participants, it provides us with ample insights on user preferences and perceptions towards touch modality for mobile gaming. As this is a pilot study , more participants wi ll be involved in follow-up studies to further validate the findings. We also find that such

ACKNOWLEDGMENT

The authors would like to thank the partI cIpants from Interface Design Department, Faculty of Creative Multimedia, Multimedia University Malay sia, who were involved in this research project. REFERENCE S [1]

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