Ioana Andreea Stanescu
email: ioana.stanescu@ats.com.ro

Antoniu Stefan
email: antoniu.stefan@ats.com.ro

Madeleine Baalsrud Jannicke

Hauge

Using gamification mechanisms and digital games in structured and unstructured learning contexts

Keywords: lesson plan, location-aware, game customization, Tingo

The transition from the pre-defined and often inflexible tools and practices of institutionalized mass-education towards dynamic and flexible learning contexts remains a challenge. Enabling rich and engaging learning experiences that consider the different progression rates and routes of each student require new approaches in education. This paper analyzes opportunities for employing gamification and digital games to construct navigable dynamic learning channels and enable pathways towards turning users into adaptive learners able to reach learning goals both in structured and unstructured contexts.

Introduction

In recent years, games have found a new application, as the era of gamification has been launched. Gamification represents the application of game-thinking, game dynamics, and game mechanics in non-game contexts, with the purpose of engaging users, increasing participation, facilitating learning, and solving problems [START_REF] Davis | Emerging Research and Trends in Gamification[END_REF]. Gamification has emerged as a strategy across various disciplines such as education, environment, government, health, marketing, web, mobile applications, social networks, etc. Applying gamification in each of these contexts require a deep understanding of the relationship between the needs of the gamification project and the appropriate choice of game elements to apply [START_REF] Deterding | Gamification: Using game design elements in non-gaming contexts[END_REF]. Research on gamification has bloomed, and design practices, such as the 6G framework [START_REF] Hunter | The Gamification Toolkit: Dynamics, Mechanics, and Components for the Win[END_REF] brought the promise of successful gamification. At the core of gamification lies the following game element hierarchy [START_REF] Hunter | The Gamification Toolkit: Dynamics, Mechanics, and Components for the Win[END_REF][START_REF] Sharp | Introduction to Game Design LiveLessons (Video Training)[END_REF]:

-Components: the specific examples of the higher-level features, such as points, virtual goods, quests, etc. -Mechanics: the elements that drive player involvement and include elements like chance, turns or rewards. -Dynamics: elements that provide motivation through features like narrative or social interaction. Even if gamification brings the promise of engagement, there are also challenges to be considered when applying gamification mechanisms, especially in educational settings. Most elements used in gamification rely on competition and rewards. In games where competition lies as the core of the experience, we can identify two main categories: (a) head-to-head competition, where players compete directly against one another; (b) Asynchronous competition, where a player competes against other players by comparing the outcomes of their play [START_REF] Sharp | Introduction to Game Design LiveLessons (Video Training)[END_REF]. These approaches cannot be applied as a universal solution. It is necessary to consider that each student has different needs and not all are motivated by competition [START_REF]Gamification[END_REF]. Therefore, other mechanics need to be identified to lead motivation and engagement. Cooperative play experiences and chance-based play provide an alternative. In cooperative play, players can work simultaneously to achieve a common goal or take turns, in order to find success, while in chance-based games use randomness and chance to enhance the variety of decisions need to make. Such implementations reflect the basic human activity matrix that ranges from solo (hobby, audience, analysis) to competitive (job, sport, criticism) and collaborative activities (community, performance, teaching) [START_REF] Koster | Theory of Fun for Game Design[END_REF]. Just like in nondigital or less technologized collaborative learning environments, where students work together on a collaborative assignment and at the same time they deepen their knowledge and their understanding [START_REF] Barkley | Major Collaborative Learning Techniques: A Handbook for College Faculty[END_REF], games have also the potential to increase participation in learning activities by enlarging availability of opportunities to collaborate; enhancing the accessibility of those opportunities, as well as the affordability [START_REF] Connolly | Collaborative Learning 2.0[END_REF].

Digital Educational Games build upon major learning theories [START_REF] Trentin | Networked Collaborative Learning[END_REF]. In line with the behaviorism theory, games deliver stimuli to learners, gather their responses and provide feedback [START_REF] Desmet | Bridging behavior science and gaming theory: Using the Intervention Mapping Protocol to design a serious game against cyberbullying[END_REF]. Following the constructivist approach, games involve learners in active processes, enabling them to construct new ideas or concepts based on their existing knowledge and experiences [START_REF] De Gloria | The Serious Game Constructivist Framework for Children's Learning, 4th International Conference on Games and Virtual Worlds for Serious Applications[END_REF]. Social constructivism is applied in games by providing diverse cultural, language, and environmental contexts in which learning can take place. Connectivism is strongly represented in virtual environments [START_REF] Isman | Connectivism Learning Environment in Augmented Reality Science Laboratory to Enhance Scientific Literacy[END_REF], where the ability to make decisions [START_REF] Leadbetter | Collaborative Knowledge in Scientific Research Networks[END_REF], as well as nurturing and maintaining connections is explored to facilitate game achievements through continual learning.

While employing gamification to stimulate learning is the latest trend [START_REF] Urh | The Model for Introduction of Gamification into E-learning in Higher Education[END_REF], the use of games in education has gained momentum in the last decade. However, designing games with a good game-play and immerse game players in a realistic setting while also encouraging re-playability is considered a true craft. Employing games in education require the consideration of the variables that influence learning and a learning theories need to be incorporated into the game design practices [START_REF] Bishop | Gamification for Human Factors Integration[END_REF]. However, promising games are for the educational setting, a significant issue that needs to be ad-dressed is the limited opportunities to tailor games for specific learning activities. Game customization remains a job for developers, even if efforts are being made to implement deeper levels of customization foe end-users [START_REF] Kleinsmith | Customizing by doing for responsive video game characters[END_REF], [START_REF] Behr | Chapter 14 -Creative Interactivity: Customizing and Creating Game Content, In Video Games and Creativity[END_REF], [START_REF] Nagle | Towards a system of customized video game mechanics based on player personality: Relating the Big Five personality traits with difficulty adaptation in a first-person shooter game[END_REF].

Learning experiences span from effortless to difficult, where the gratification of accomplishment is delayed [START_REF] Burke | Gamify: How Gamification Motivates People to Do Extraordinary Things[END_REF]. The challenge is not to motivate; it is to support them finding a path to success. Coupled with technology advancement, at strategy level, the priorities for Education and Training 2016-2020 focuses on more open and innovative learning and teaching; sustainable and efficient investments in educational systems; relevant and high quality skills and competencies; inclusive education, equality, and non-discrimination; as well as strong support for educators.

The European Qualification Framework [20] also recognizes the need to support validation of non-formal and informal learning towards core skills such as literacy, numeracy, science, foreign languages; and horizontal skills such as learning to learn, social and civic responsibility, creativity, to support learners in finding personal fulfilment, and later in life find employment and engage in society. All require new approaches in pedagogical practices and experimentation in smart, scalable, inclusive learning environments.

Key to addressing these challenges is the flexibility and elasticity of the learning space, of its contents and assessment methods that enable the learning space be reshaped based on learners' needs, performance, abilities, as well as on the learning objectives that have to be met. Digitally supported pedagogy today still relies on predefined (rigid) learning contents and assessment methods, and learning systems that are too assistive, leading to a distorted learning outcome. They do not adopt studentcentred learning and do not present the required level of flexibility to accommodate both structured and unstructured learning.

In the context of this paper, structured learning contexts are constructs that are modeled by teachers in order to implement a certain learning plan. Unstructured learning contexts are constructed by students based on given assignments. Constructing consistent, yet dynamic learning spaces is an increasingly important issue in the context of the advancement and expansion of technologies for learning and skill development.

This paper reports work in progress on designing gamified lesson plans that are applied in structured and unstructured learning contexts. This approach creates new levels of flexibility in reaching learning objectives by employing emerging gamification mechanisms and digital educational games.

CONSTRUCTING STRUCTURED AND UNSTRUCTURED LEARNING CONTEXTS

The shift towards more flexible learning implies the adoption of new methodologies and practices. The emergence of gamification and gaming technologies offer opportunities to construct new approaches to learning, giving learners more freedom, strengthening collaboration skills, and stimulating their creative mind. This section presents the transition from a traditional classroom-based approach to a gamified approach that employs technology to build specific language competencies. In the context of this paper, structured learning is learning that is continuously regulated by the teacher; while an unstructured learning context occurs when the teacher initiates the learning, but does not impose the steps to achieve the learning objectives and meet the assessment metrics.

Classroom-based lesson plan

A significant part of the teaching activity relies on traditional methods, while the technology-oriented generations expect more engaging learning methods. Even if significant efforts are being made, the tradition from teacher-centers to studentcentered education remains challenging. To address it, this paper follows the transition from conventional teaching methods to new approaches that integrate gamification and games as consistent stimuli for motivation and engagement.

Table 1 presents a lesson plan created for advanced English students in the 10 th grade. The lesson plan details the curriculum objectives, the language skills that will be developed, the general and the specific objectives of the lesson plan, as well as the specific set of activities that will be carried out during the class.

General objectives of the lesson:

-To improve the student's vocabulary with words related to history, city architecture and civic responsibility -To develop communication and collaboration skills -To assess comprehension of oral and written messages -To enable students to use previous knowledge -To enhance civic engagement Specific objectives to be achieved by the end of the lesson:

-Students will be able to use vocabulary related to history and city architecture -Students will be able to recognize positive, negative, and neutral comments -Students will be able to describe historical events and historical figures -Students will be able to comprehend the oral and written messages given by the teacher concerning the history and architecture of Târgoviște City -Students will be able to present ways in which they can participate in the life of the local community and can get involved in shaping the community's future. The students work individually. The students are asked to go scan a text that present the architectural styles of the buildings in the city and find out what is the topic of each new paragraph. After reading the text, the students do the exercise at the bottom of the text.

Activity 3 -Speaking, Listening

The students form pairs. They talk about different categories of buildings from Târgoviște. They are asked to match names with building images. After discussing in pairs, the students present their feedback to the rest of the class.

Activity 4 -Listening, Speaking

Before listening to a text on civic responsibility, the students make predictions about what they are going to hear.

The teacher reads the text on civic responsibility. Afterwards, the students discuss if/ how their perspective on civic responsibility has changed.

Activity 5 -Writing

The teacher asks the students to write a short composition on the buildings of Târgoviște, historical figures and civic actions that can be taken to preserve the historical heritage of the city and support its future development.

Gamified learning

Starting from the lesson plan presented above, to ease the transition to emerging teaching methods, a gamified approach has been constructed. Table 2 and Table 3 present a set of activities that can be implemented to enhance student engagement and motivation to learn.

Table 2. Structured indoor learning Organization of the class Activity: "Fill-in exercise" -Writing, Reading, Listening Students will work in groups of four. Each group will choose a name for their team. Each team selects a letter. Each letter is associated with a different set of fillin exercises. The set of exercises is divided into several levels of difficulty:

Level 1. Vocabulary practice. (10 points/ 1 badge) The students will fill in the blanks with words they learnt in previous lessons. 1 point is given for each correct answer. 1 badge is given if the set of exercise is completed without errors.

Level 2. Vocabulary practice. (20 points/ 2 badges)

The students will match a given set of new words with the blank spaces. 2 points are given for each correct answer. 2 badges are given if the set of exercise is completed without errors.

Level 3. Vocabulary practice. (30 points/ / 3 badges)

The students will listen to an audio message/ watch a clip presenting the historical buildings in Târgoviște City and fill-in the blanks. 3 points are given for each correct answer, as the level of complexity increases. 3 badges are given if the set of exercise is completed without errors.

If the general and specific objectives of the lesson plan are extended to include grammar practice, the following levels can be added:

Level 4. Grammar practice. (20 points/ 2 badges)

The students will fill-in the blanks with adjectives from a given list using the right degree of comparison.

Level 5. Grammar practice. (30 points/ 2 badges)

The students will fill-in the blanks with the right tense of the verb in brackets.

To make the activity more interesting, hints can be places in the classroom or within the school. The team that gathers the largest number of hints will get extra points. Time limits can be added to certain activities, in order to be able to comply with the estimated time of the lesson.

The team that collects the largest number of points or the largest number of badges wins the game. Special credit is given to the teams that have obtained best results per level.

Table 3. Unstructured outdoor learning Activity: "Puzzle" -Writing, Reading, Listening, Speaking Students can play and collaborate to put together a map of Târgoviște City. Students will work in groups of six. Each group will choose a name for their team. Each team selects a different type of map: historical buildings, churches, modern buildings, favorite shops, memorial houses, parks, local markets, etc. All the documentation process is carried out outside the classroom. The role of the teacher is to set the goals of the game, without setting up rules or restrictions on how the research should be carried out or how the project should be elaborated.

Each team has to document their project with information and pictures of the buildings they have identified.

A team obtains or loses points based on the following criteria: -Number of buildings included in the project. (10 points per building) -Quality of information. (1-5 points per building)

-

The originality of the work. E.g. if pictures are taken by the team members and not from the Internet. (30 points) -Spelling mistakes. (-2 points per mistake) -Grammar errors. (-5 points per mistake) Evaluation is carried out by the competing teams and not by the teacher.

An example of smartphone app that provides information about points of interest around the current location of a user is Field Trip. The application is a good indication of what can be achieved in terms of user experience for the students (https://play.google.com/store/apps/details?id=com.nianticproject.scout). However, it is not tailored for a formal learning environment and does not provide any kind of APIs or reporting that could be used by teachers to select the list of relevant topics that should be provided or to understand how students have engaged with the information and long they have been following a particular topic.

Blending technology into unstructured learning contexts

One of the key challenges in providing students with unstructured learning is to set up an environment where users can have access to on-demand knowledge that is relevant to their current context and desired learning outcomes.

Existing technologies offer opportunities to create rich learning experiences at user level, building upon wide databases and supporting large-scale reuse. The tools proposed therein are: a. DBpedia, a project that provides semantically classified information that can be queried using a vast number of descriptors, including geo location. Because the resources contained in the datasets are classified semantically, it provides a straightforward way to retrieve these resources based on specific topic of interest and also to locate related content using knowledge graphs. b. Wikipedia, the premier online open encyclopedia offers basic API functions that can search for articles that are in a specific radius from a particular geo location (https://www.mediawiki.org/wiki/Extension:GeoData#API). The limitation of this service is that it cannot be used to filter the results based on particular topics of interest. In some context this could be beneficial because students are exposed to the entire set of information that is available, but it can also be a factor that distracts their attention from the desired learning outcome. c. Wikimapia, a service that aims to describe and categorize physical locations.

Game-enhanced learning with Tingo

Tingo is a Digital Educational Game developed by Advanced Technology Systems, Romania (http://desig.ats.com.ro/). The game was created to support foreign language learning, while coupling specific curricular competences and game activities.

A significant issue that occurs when teachers aim to employ digital games as support tools for learning is to adapt the game to the specific learning objectives within a lesson plan. To address this issue, the Tingo game has been designed to enable a basic level of customization, allowing teachers to create simple learning contexts. The applied scenario builds upon location-aware technology.

Starting from a simple map, several game objects can be added to create a fantasy map of the city (Fig. 1). Information dragged from the tools presented in the above section and GPS coordinates can be added for each of the buildings included in the map. When the player explores the virtual world, the background images changes color for the areas the players has visited (Fig. 2). When the player physically reaches a building, the game uses GPS coordinates from the device to determine the building and change its color on the map. If available, additional localization devices such as Bluetooth beacons or Wi-Fi base stations can also be used (Fig. 3).

In Tingo, individual players can set up their own bookcase. To collect books, players need to complete additional quests. Players can combine individual bookcases to form a public library.

To increase motivation, the game enable players to set up an individual vocabulary. As they progress in the game and learn new words, their individual vocabulary becomes larger and larger. The game displays a scoreboard with the following categories of players: (a) players that have the largest collection of words; (b) players that have the largest number of unique words that do not appear in other players' vocabulary; and (c) players that have the largest number of similar words.

Starting from specific competences that are targeted (Table 4), the activities presented in Table 5 have been created using the wizard feature of the game. The game displays several buildings and the player has to guess their category.

The player is requested to match different activities with building categories.

1.2

The game displays a text message and the player has to act upon the information the game has provided.

1.3

The game displays a text message and the player has to identify words from a certain category: e.g. nouns, verbs; or categories of buildings. 1.4 The player listens to an audio message and is required to perform certain tasks, such as click on the building that has been described in the audio message. 1.5

The game displays text messages that provide information on historical buildings in Târgoviște and the player is requested to classify them based on their architectural profile, the year they were built, etc. 1.6

The player is requested to identify the chronological order of the historical facts that are presented in several written or audio messages.

These scenarios can be extended to support, for example, problem based learning. By coupling learning foreign languages with other disciplines such as math, the lesson plan on the architecture of the Târgoviște City can include specific tasks that address math topics.

Discussion and Next Steps

Students will invariably experience different progression rates and routes, which often lead to different learning outcomes than those expected. This can be a consequence of several factors including the pre-defined and often inflexible tools and practices of institutionalized mass-education, but above all else emerge two key considerations: on one hand, learning is a choice, an act of personal agency and even if the best blend of technologies is available, without sustained motivation, learners will not truly engage in deep learning processes; on the other hand, when technologies are not available or are not easy to integrate into learning spaces, the experience might prove too frustrating even for motivated learners.

To address these challenges, it is necessary not only to turn ICTs into navigable dynamic learning channels, but also to enable pathways towards turning users into adaptive learners able to reach learning goals without a high dependency on certain technologies. Technology is a guide for learners and a mean to reach learning goals. Therefore, technology dependency should be avoided. The aim is to foster selfregulated learning by assisting learners in how to comprehend and realize when they do not know something and to stimulate discovery such that learners seek out the necessary knowledge or information. The immediate benefit of such a learning environment is that it affords ambient leaning including adaptive and personalized teaching and assessment.

This approach contrasts to recent developments and solutions where the software is too assistive letting the learner know what is 'needed' in every step of the learning journey rather than letting the individual conduct reflective and summative learning. Removing agency from the equation of learning (and teaching) has implications from the pedagogical perspective. It limits the quality of the learning experiences by creating automatons and the consequential reliance of learners becoming highly dependent on software.

Instead, the approach proposed in this paper follows a completely different paradigm, where learners are given the freedom of choice based on a plug&learn approach (e.g. smartphone apps; digital games). It considers the fact that the outcomes of learning experiences that occur outside of formal, structured settings are not assessed and valuable information about the learner is lost. Moreover, the solution proposed herein builds upon the fact that many students own mobile devices. This offers a significant opportunity for bring-your-own-X (device, cloud, applications, etc.) enabling individuals to find one tool that performs every function they need, removing the hassle of working with problematic tools that do not address all their needs.

The paper presents lesson plan scenarios that employ gaming technology to construct engaging learning experiences. Future work involves the testing of the prototype and of the scenarios with students from different high schools, with the purpose of extending the learning scenarios for problem-based learning and enhancing the functionalities provided by the Tingo game.

  The teacher asks the students to comment on the role of the Târgoviște City as the former capital of Romania Activity 2 -Reading

Figure 1 :

 1 Figure 1: Map of Târgoviște City in the Tingo game

Figure 2 :Figure 3 :

 23 Figure 2: Student activity within the game Figure 3: Student activity in physical locations

Table 1 .

 1 Classroom-based English lesson plan Lesson

topic: Târgoviște City -past, present and future

	Subject: English	Grade: 10 th
	Level: Advanced	Time: 50 minutes (1 course)
	Location: Classroom	ICT: PowerPoint presentation, video clips
	Objectives

set in the national lan- guage curriculum for the 10 th grade, advanced level Language skills targeted by the lesson plan

	Objective 1. Comprehend oral and	Listening: receptive skill
	written messages in diverse contexts	Reading: receptive skill
	Objective 2: Speaking or writing on	Speaking: productive skill
	diverse topics	Writing: productive skill
	Objective 3: Oral or written collabo-	Speaking: productive skill
	ration	Writing: productive skill

Table 4 .

 4

	Curriculum-based specific competences

Acknowledgement

The work presented herein is partially funded under the Horizon 2020 Framework Program of the European Union, BEACONING -Grant Agreement 68676 and by Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii (UEFISCDI) in Romania, Contract no. 19/ 2014 (DESiG).


Sinjae Lee

Sangbin Kim

Junghyun Han
email: jhan@korea.ac.kr

Promoting Stretching Activity with Smartwatch -A Pilot Study

Keywords: Smartwatch, Physical activity, Stretching, Motion recognition, Hidden Markov Model, Gamification

It has been claimed that wearable devices are useful for healthcare applications by providing functionalities such as idle alerts, pedometer, heart-rate measurement, and calorie calculation. However, these functionalities have the limitations of providing only passive assistance. In order to prompt users to do physical activities, we developed a prototype application for active assistance, which works on smartwatch devices. It guides users to stretch their arms periodically during their daily lives. For effective guidance, we integrated motion recognition and gamification elements. We performed a user study to confirm the usefulness of our approach.

Introduction

In recent years, the field of wearable technology has grown rapidly especially for wrist-worn devices such as smartbands and smartwatches. Since the devices are integrated with not only high-performance CPU and GPU but also accurate micro-electromechanical system (MEMS) sensors, it is possible to implement various services on user's wrist, which include idle alerts, pedometers, exercise recording/management, and calorie monitoring, claiming to assist in healthcare.

The medical community has reported that sedentary work over many hours can be very harmful to health [START_REF]AOA: Standing Up for Your Health[END_REF] [START_REF] Owen | Too much sitting: the population-health science of sedentary behavior[END_REF]. It is generally recommended that workers do not remain in the same posture for long periods at the workplace [START_REF]COMCARE: Sedentary Work[END_REF] [START_REF] Pronk | Reducing occupational sitting time and improving worker health: the take-a-stand project[END_REF], and the public have thus taken an interest in wearable devices that can help in this context. Such devices often adopt an idle alert function to tell users to move or change their posture. However, we believe it is difficult for these functionalities to effectively encourage physical activities. We call them passive assistance. In this paper, we propose an active assistance functionality that can effectively prompt the users physical activities.

Promoting physical activities has mainly been studied from the perspective of games [START_REF] Consolvo | Goal-setting considerations for persuasive technologies that encourage physical activity[END_REF][5] [START_REF] Tabak | Promoting daily physical activity by means of mobile gaming: a review of the state of the art[END_REF]. However, game activities have their own limitation that people are made to get fully devoted to them in a certain place and for a certain period of time. Our approach presented in this paper aims at promoting physical activities using wearable devices in daily environments.

We have developed a prototype application based on smartwatches. It prompts physical activity by informing the users that it is time to stretch, guiding and evaluating their motion, and providing feedbacks. Additionally, gamification elements are added to further motivate the users' activities. Our approach is the first study to prompt physical activity and evaluate it using a wearable standalone device.

Active-assistance operations

The objective of our work is to investigate whether it is possible to effectively prompt physical activities by promoting arm stretching with the assistance of a wrist-worn smartwatch (Figure 1-(a)). In the smartwatch, the watchface mode provides reminder when the user has not stretched for a certain period of time. See Figure 1-(b). In this study, the watchface mode is set to provide reminders between 10am and 6pm, when the user is assumed to be working at his or her chair. The stretching reminder is set off one hour after the last stretching time. The user can perform arm stretching according to the application's direction or turn down the reminder message. The reminder time is then updated to one hour later.

Figure 2 shows the arm-stretching flow guided by the application. If the user accepts the reminder message, stretching guide is provided, as illustrated in Figure 2-(a). The first layer of the guide provides character images together with simple text whereas detailed text is given in the second layer that can be accessed by scrolling. The way to stretch is explained with spreading/shrinking wave animation of circles, as shown in Figure 2-(b) and-(d). At the peak state of stretching, the user is supposed to retain the stretched posture for five seconds. provided at the start and end times so that the user does not need to take a look at the display during stretching.

Evaluation and feedback

The user's stretching motion can be represented by sequential time series data. We used a Hidden Markov Model (HMM) algorithm [START_REF] Françoise | A multimodal probabilistic model for gesture-based control of sound synthesis[END_REF], which processes sequential data in real time on embedded systems. We acquired the accelerometer data at 100 Hz and used a Kalman filter to compensate for the noise in the raw sensory data. The observation vector, containing acceleration and some processed data, was evaluated in real time during the stretching action. When the users action was done, we compared the probability given by the motion recognition algorithm with the proper threshold to determine whether the user succeeded or failed. For this purpose, we need off-line pre-training stage and per-person training stage. Ten volunteers were involved in the pre-training stage. Each volunteer provided ten motions for the vertical stretch. We assume that the arm movement is symmetric and can safely rely on the data from a single sensor on one wrist. We also added gamification elements. When user succeeds, the application displays the progress bar for the pre-set daily goal. See Figure 3-(a). The progress bar is increased by 20% per successful stretching motion. When the goal is achieved, the application congratulates the completion of daily goal and displays a virtual reward. In the current implementation, it is the gold medal, as shown in Figure 3-(c).

User study: Result and Discussion

We conducted an experiment to assess our approach of providing stretch reminders, guiding the motion, and evaluating the user's motion. The smartwatch used in the experiment is Samsung Gear S21 with Tizen OS (wearable profile version 2.3.1). The prototype application is implemented in C++ for the native environment 2 . Before and after the experiment, participants were asked to fill in questionnaires. We informed the participants that the acquired data would only be used for the present study.

Procedure

We recruited 17 participants (15 males and 2 females) aged 23 through 41 (with M 29.875 and SD 4.177). They included graduate students, engineers, and office workers. The participants were paid $10 for their involvement. Nine out of them had experiences in healthcare services based on mobile or wearable devices.

We first conducted an initial survey before the experiment. Then, after being instructed in the usage of the application, the participants performed a training for stretching activity in order to enhance the motion recognition rate. The experiment lasted three days, during which the participants wore the device and continued their normal daily activities. The application recorded the log data during the experiment, e.g., how many times stretching was done, whether the user failed or succeeded, etc. After the experiment, we extracted the log data from the device and asked the participants to fill in the final questionnaire.

Questionnaire and result

The initial questionnaire asked participants how much time they typically spend doing sedentary work and how frequently they do stretching per day. The participants do approximately 8.5 hours of sedentary work and stretch on average 1.84 times per day.

We analyzed the recorded log data. For three days of experiment, the participants received on average 7.147 reminder messages per day, of which 64% were accepted. On average, they attempted 18.201 stretches per day. In the three-day experiment, the goal (at least five intermittent stretching motions) was achieved for two days on average. See Data analysis part of Table 1.

The result of the final questionnaire is shown in Questionnaire analysis part of Table 1: (1) The "effectiveness of stretching" is meant to measure the personal perception on how much the muscles seem to be relaxed as a result of stretching;

(2) With respect to the "effect of gamification," the participants were asked how much they were motivated by the reward, i.e., gold medal for achieving daily goal; (3) The final question asked the participants whether, if given a chance, they intend to use same application in the future.

Discussion

In general, we received positive responses from the participants. According to the results, the participants performed stretches as much as 18 times per day. Recall that, in the initial survey, they answered that they stretched on average 1.84 times over 8 hours. They also appraised highly the effectiveness of the stretchpromoting system and most of them wished to use this kind of application again.

The gamification element was expected to motivate the user to perform stretching more actively, but the score on "effect of gamification" (M 3.059 and SD 0.899) does not lead to the conclusion. It can be analyzed from two perspectives. First of all, adding gamification elements might not be effective for prompting physical activities, as claimed by [START_REF] Zuckerman | Deconstructing gamification: evaluating the effectiveness of continuous measurement, virtual rewards, and social comparison for promoting physical activity[END_REF]. Secondly, the reward in the current prototype system, the gold medal, is too simple to be assessed. When the prototype application is extended into a pervasive game, a more elaborate rewarding system could be added and evaluated more formally.

Conclusion

We have presented an attractive approach to encourage user's physical activity by using smartwatch-based prototype application. During the experiment, participants wore a smartwatch which reminds stretching time periodically. The experimental results show that participants were made to conduct more stretching activity and provided positive feedback for our approach although the static time-based reminder might be able to annoy them when they do not want to stretch.

We concluded that it is possible to encourage user's physical activity with an active assistance manner for people wearing smart wearable devices. We are currently extending the system and also designing more elaborate experiments.

Fig. 1 .

 1 Fig. 1. A smartwatch and its interface. (a) Smartwatch. (b) The watchface mode reminds the user of stretch.

Figure 2 -

 2 (c) shows the five-second countdown animation. Haptic feedback is

Fig. 2 .

 2 Fig. 2. User interface for arm-stretching flow.

Fig. 3 .

 3 Fig. 3. Gamification elements. (a) For the success case, the progress bar is displayed at the boundary area. (b) The fail case. (c) Daily goal achievement.

Table 1 .

 1 Results of the experiment. The values of the Questionnaire analysis show 5-point Likert-scale from 1 (low) to 5 (high).

	Data analysis	M	SD
	Number of reminders per day	7.147	2.398
	Number of stretches per day	18.201	7.968
	Number of daily goal achievement	2.000	1.110
	Questionnaire analysis	M	SD
	Effectiveness of stretching	4.000	0.791
	Effect of gamification	3.059	0.899
	Intention to reuse	4.471	0.514

http://www.samsung.com/global/galaxy/gear-s2/

https://developer.tizen.org/development/api-tutorials/native-application

Acknowledgement

This work was supported by Institute for Information & Communications Technology Promotion (IITP) grant funded by the Korea government (MSIP) (No. R0115-15-1011) and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. NRF-2016R1A2B3014319).


Nikitas M Sgouros
email: sgouros@unipi.gr

Geometric Representations for Subjective Time in Digital Narratives

Keywords: Time, Narrative, Visualization, Experiential aspects

Subjective time refers to our living experience of time. We develop subjective timescapes i.e., spatial representations for time as experienced by story characters. Each such timescape describes how a character perceives and shapes story time. We show how these spatial constructions are compatible with relevant psychological and phenomenological studies on subjective time. Timescapes allow us to model characters as operating from particular temporal perspectives mediated by memory and anticipation at various points in a story and to provide geometric mappings of these concepts. We apply these ideas in a visualization environment for digital narrative plot structures.

Introduction

Most of the current research and applications of time focus on representing and managing "clock" time, i.e. fixed periodic structures such as the 24-hour standard or the calendar system. However, there is another equally important notion of time, that we call "subjective" time, and describes our awareness of precedence or succession, duration, simultaneity and tempo of events, the feeling of presence, and the establishment of temporal perspectives on events and behaviour. In contrast to its clock counterpart, subjective time is qualitative in nature [START_REF] Wittmann | Felt Time: The Psychology of How We Perceive Time[END_REF], different for each individual and with no rigid linear structure. Subjective time exerts considerable influence on motivation, planning and execution of purposeful activity [START_REF] Baron | Our Concept of Time[END_REF]. We describe the construction of subjective timescapes, i.e., spatial representations for the experience of time in story characters. We develop geometric perspectives for representing the flow of time, temporal dilation and segmentation in episodes. We provide geometric mappings that make these phenomena examinable and allow the creation of alternative character-centric micro-narratives describing how characters experience time. Current narrative systems focus on supporting inferential aspects of stories by reasoning about plans and actions from character goals using variants of plan-based AI methods [START_REF] Young | Plans and planning in narrative generation: a review of plan-based approaches to the generation of story, discourse and interactivity in narratives[END_REF]. They seek to formalize the notion of clock time and to provide means for reasoning about the temporal aspects of knowledge. Time in their stories is something external and disassociated from what is happening in the story. In contrast to these systems our approach seeks to represent how story events interact with the experience of time in characters.

Character state and subjective time

A narrative can be analysed as a sequence of events describing the goals and actions of a set of characters and the complications arising from them. Given such a goal-oriented structure we represent character state in terms of his current disposition towards various goals, i.e. his perception of how near or far he currently is towards their adoption and/or attainment and of how interrelated these goals are. We model character state as a unit vector in a 2-D real vector space lying on an horizontal unit circle centered on the character (see Fig. 1(a)). Thus, character state and goals are mapped to particular directions of motion in space. This configuration reflects the character's perception of goal-driven behavior as motion in a particular direction. Pairs of goals that are opposite to each other and, therefore, pose a dilemma for a story character, are mapped to orthogonal vectors in this space and define a basis for this vector space. The configuration of such a basis encodes the semantic opposition of its goals as a left-right antithesis that reflects a common story metaphor of a dilemma as a forking path of two orthogonal directions forward. As an example, Figure 1(a) depicts the state and goals for a character X. X is confronted with two possible and contrasting goals (becoming either good or bad). We represent such a moral viewpoint with a basis M consisting of two orthogonal unit vectors (vectors are written in bold) good and bad denoted in red in Fig. 1(a). A state X 0 of X is a vector which can be described in terms of M as a linear combination of the vectors good and bad. Such a combination indicates that X has two potential goals of being either "good" or "bad" while also describing his current disposition towards them. By disposition we refer to the distance of his current state from either of the goal vectors in M, which reflects how close he is towards adopting or achieving that particular goal. This distance is captured by the dot product between his current state vector and the particular goal vector. X can change his disposition towards his goals. Such change is represented as a rotation of his state vector. Rotation can be instantaneous, as in the case of character decisions, or gradual, as a result of action execution. For example, by reneging on a promise X can change his state from X 0 to X 1 , thus rotating his state vector closer to the bad goal (see Fig. 1(a)) and increasing his disposition of achieving this goal. We model the perception of state change from the perspective of the character involved as being proportional to the angle of rotation between his initial and resulting state.

We develop two main structures for representing subjective time. The first one, which we call clock time (C-time), refers to the temporal placing of events by an external observer using a clock. We represent the C-time for such an event as a point on the z-axis of a 3-D coordinate system (see Fig. 1(b)). We use C-time to signify that an outside uninvolved observer experiences E as preceding all events with higher z-coordinates and succeeding all events with lower ones. Also important is the difference between the C-times of successive events as this indicates the amount of time such an observer perceives as having expired between two successive events in relation to the time intervals between the other pairs of successive events in the sequence. Consequently, C-time exhibits the linearity of clock time. The second structure of time, which we call subjective time (S-time), is different for each character involved in the event sequence and corresponds to his perception of the temporal features (placing, duration, simultaneity) between successive events at each point in the sequence. More specifically, we represent each event by the effects it has on the states of the characters. Therefore, each event is a slice of C-time represented as a unit circle (such as the one in Fig. 1(a)) centered on the C-time axis and vertical to it. Each such circle contains the character states that result from the event actualization. The representations of all events are stacked on a cylinder of unit radius and height h, where h is equal to the difference between the C-times of the last and the first event in the story. We model the trajectory of S-time for character X by the sequence of the geodesics (shortest paths) on the surface of this cylinder formed by connecting the endpoints of successive state vectors of X. The duration of the S-time for X between any two successive events E1 and E2 is equal to the length of the geodesic connecting the endpoints of his state vector at events E1 and E2. Let A and B be the endpoints of the state vector for X at successive C-times t 0 and t 1 , respectively, where t 1 > t 0 (see Fig. 1(b)). The length L AB of the geodesic between A and B represents the duration of the S-time interval separating successive events at clock times t 0 and t 1 according to X. In order to compute L AB let us assume that B at t 1 results by an event that forces X's state at t 0 to transform to the one at t 1 following a helical trajectory with a rotation angle of φ radians (0 ≤ φ < 2π) around the z-axis and a simultaneous translation of (dt) AB units on the z-axis where (dt) AB = t 1 -t 0 is the C-time interval between A and B. If we then flatten our event cylinder to a square we compute L AB as: L AB = (dt) 2 AB + φ 2 . According to this relation S-time maintains the phenomenology of the flow of time in which events seem to constantly approach an agent from the future, are actualized in the present and recede to the past because S-time duration between two events is proportional to the duration of the C-time (dt) AB separating them. Furthermore, S-time duration between successive events for X is proportional to the rotation angle φ separating X's state vectors in these events. Because we model X's perceived amount of state change among these events as being proportional to this angle φ, the duration of the S-time between them is also proportional to the change in X's state. Consequently, between two pairs of successive events separated with equal C-time intervals, X will perceive the pair in which his state rotates more as lasting longer than the other one. This allows us to embed in a character an experience of duration compatible with the one posited by the contextual change model in the psychology of time in which estimates of duration of an event in which a person does not need to estimate its duration is proportional to the number of changes observed during an interval [START_REF] Zakay | Relative and absolute duration judgments under prospective and retrospective paradigms[END_REF]. We are not interested in the absolute value of S-time, only in the qualitative relations (comparisons and proportionality) between various S-times. Our ability to generate and process temporal experiences presupposes our ability to apprehend event sequences as episodes (i.e. coherent event sequences that are extended in time). We adopt the phenomenological notion of temporality in which coherency refers to the meaning established by the character for the events in question [START_REF] Husserl | Phenomenology of Internal Time Consciousness[END_REF]. We use the notion of distance between the state of a character X and a goal in his goal space, as captured by the dot product between these two vectors, to establish our notion of temporal coherency. In particular, during each event X experiences his state as staying invariant, moving closer or away from a goal G. We capture this experience by comparing the value of the dot product between G and the agent state vector at the current C-time point t i with its corresponding value at the previous C-time point t i-1 in the event sequence. If the value at t i is greaterthan, less-than or equal to the previous one at t i-1 then the agent experiences his state to converge, diverge or stay invariant, respectively, with respect to G. A sequence of events in which the agent experiences his state to only converge, diverge or remain stable with respect to a goal forms an episode.

An Example

Our story example involves three characters; Joe, Bob and Ann. This story plot has been automatically produced by QuNE, a narrative generation system based on spatial representations of purpose and quantum theory [START_REF] Sgouros | Psychagogy and quantum theory as conceptualizations for serious entertainment and its narrative[END_REF]. The goal structure (see Fig. 2(a)) motivating their behaviour consists of five bases. The first one is Morality (which is common to all three characters with two vectors good and bad). We also use two bases describing what it means for Ann to try to marry or to forget any of the other characters (bases AnnJoe with marryAnnJoe and forgetAnnJoe and AnnBob with marryAnnBob and forgetAnnBob for Joe and Bob respectively), and two bases describing such an involvement for Joe (bases JoeAnn with marryJoeAnn and forgetJoeAnn) and for Bob (basis BobAnn with marryBobAnn and forgetBobAnn). The orientation of these bases indicate that for both Joe and Bob trying to marry Ann is regarded as primarily 'good' while forgetting her as primarily 'bad'. Ann has a positive view for marriage since for her trying to marry either Joe or Bob is definitely 'good' and forgetting either of them is definitely 'bad'. Initially both Joe and Bob are more prone to decide to try marrying Ann. Ann seems more likely not to try marrying either one of them. There are four possible story developments: Date, Serenade, Duel and Marriage. Date involves Ann and one of the other guys causing each one of the state vectors involved to rotate by a random angle (dating is unpredictable). Serenade results in increasing the probability for Ann to decide and marry her serenader. Duel implicates two guys resulting in the winner trying to marry Ann and in the loser deciding to forget her. Finally, Marriage occurs when both characters decide to do so. Bob seeks to persuade Ann to marry him therefore he seeks through his actions to make her state parallel with marryAnnBob. At E1 Joe (the loser) decides to forget her. This is indicated by the rotation of his state from J 1 to J 2 which becomes parallel with forgetJoeAnn (trajectory J 2 J 8 ). Bob serenades Ann four times (E2-5, trajectory B 2 B 6 ) and this arouses Ann's interest for Bob by rotating Ann's state gradually closer to goal marryAnnBob (trajectory A 1 A 5 ). In E6 Bob and Ann go on a date which makes Bob waver on whether he should try to marry Ann (in B 6 B 7 his state vector rotates away from marryBobAnn), even though Ann seems to like him more (in A 5 A 6 her state rotates closer to marryAnnBob). In E7 both characters decide to marry. This is indicated by the rotation of Bob's state from B 8 to B 9 becoming parallel to marryBobAnn and Ann's from A 7 to A 8 becoming parallel to marryAnnBob. Each character experiences a different micro-narrative stemming from his partitioning of time into episodes during the event sequence. In particular, at the end of the story Joe divides his experience into two episodes. The first one consists of the sequence J 0 J 1 and the second one of J 2 J 8 . This is the case because between J 1 and J 2 Joe reaches the goal of forgetting Ann. Ann partitions her experience in three episodes. The first one consists of the sequence A 0 A 6 , the second one of A 6 A 7 , and the third one of point A 8 . This is the case because in A 6 Ann's state changes from converging towards marryAnnBob to becoming invariant with respect to it, while in A 8 Ann decides to marry Bob. Analogously, Bob partitions his experience in five episodes, B 0 B 1 , B 2 B 6 , B 6 B 7 , B 7 B 8 and B 9 . Other micronarratives also emerge. For example, during E1-7 Joe perceives Ann's state to rotate away from his and vice versa signifying a growing rift between the two, while on the other hand the states of Bob and Ann move close to one another signifying a gradual rapprochement. In general, subjective duration for Ann and Bob is greater than Bob, since the length for J 0 J 8 is less than either A 0 A 8 or B 0 B 9 indicating greater effort for Ann and Bob than Joe.

Fig. 1 .

 1 Fig. 1. (a) Atemporal representation for the state of character X on the unit circle (b) C-time interval (dt)AB and S-time segment AB for X corresponding to events at C-times t0 and t1. X's state follows the helical trajectory of the S-time curve from A to B by simultaneously rotating with an angle φ and translating by (dt)AB on the z-axis.

Fig. 2 .

 2 Fig. 2. (a) Initial configuration for the example love story ('≡" denotes coincident vectors) (b) Subjective timescapes for the characters in the example love story.

  Fig. 2(b) depicts the S-time structure of this story based on the configuration of Fig. 2(a) that is reproduced as the Event 0 (E0) circle in Fig. 2(b). Fig. 2(b) depicts the trajectory of Ann's state by the sequence A 0 A 8 , the one for Bob with the sequence B 0 B 9 and the one for Joe as J 0 J 8 . Most of these pairs of successive points (e.g. A 4 A 5 ) are connected with line segments whose length indicates the duration of the S-time interval between successive events for the character involved. The ones not connected (e.g. B 1 , B 2 ) describe instantaneous character decisions and therefore lie on the same event circle. Fig. 2(b) assumes equal C-time intervals between the story events. E1 corresponds to Joe and Bob contesting for Ann. Bob wins and decides to try marrying Ann (goal G). This is represented as the instantaneous rotation of his state at E1 from B 1 to B 2 where at B 2 it becomes parallel with marryBobAnn.

Acknowledgments. Presentation of this paper was partially supported by the University of Piraeus Research Center.


Simone Mora
email: simone.mora@ntnu.no

Tomas Fagerbekk

Matthias Monnier

Emil Schroeder

Monica Divitini
email: monica.divitini@idi.ntnu.no

Anyboard: a Platform for Hybrid Board Games

Keywords: Hybrid Game, Pervasive Game, Design, Prototyping, Platform, Tangible Interface

Making hybrid board games that mix the interactivity of video games with the social impact of board games is challenging. While the design process needs to take into account elements from the digital and analog domains, building prototypes requires dealing with diverse technologies in the field of Tangible Interfaces and Interactive Tabletop and Surfaces. Anyboard provides theoretical tools to map traditional board game interaction to the hybrid medium and lightweight technology tools to facilitate game prototyping. Our platform provides augmented game pieces that work with traditional cardboards, allowing designers to easily build collaborative interactive games without requiring engineering skills.

Introduction

Despite the popularity of computer games, board games still represent a significant part of the market [START_REF] Costikyan | Don t be a vidiot: What computer game designers can learn from non-electronic games[END_REF]. The reason lies in board games providing a more human-oriented experience compared to computer games [START_REF] Mandryk | False prophets: exploring hybrid board/video games[END_REF]. Playing board games is indeed a social ritual where families and friends get together; having low entry-barriers for cost and skills, board games represent a cross-generational form of entertainment.

Over the last twenty years, research has pointed at combining the interactivity of computer games with the benefits of board games [START_REF] Mandryk | False prophets: exploring hybrid board/video games[END_REF][START_REF] Magerkurth | Pervasive games: bringing computer entertainment back to the real world[END_REF] creating interactive and augmented board games; hereafter referred as hybrid board games. For a review see Haller et al. [START_REF] Haller | Tabletop games: Platforms, experimental games and design recommendations[END_REF]. Hybrid games have been extensively implemented using interactive surfaces such as tabletop computers, recently complemented by novel technologies in the field of Multi-Display Environments (MDE) [START_REF] Mueller | Capture The Flag: Engaging In A Multi-Device Augmented Reality Game[END_REF] and Around-the-Device Interaction (ADI) [START_REF] Garcia-Sanjuan | Around-Device Interactions: A Usability Study of Frame Markers in Acquisition Tasks[END_REF]. In hybrid games, large interactive surfaces recreate the social affordances typical of board games, whilst the use of active or passive playing pieces preserve physical affordances similar to traditional game pieces. However these technologies pose several constraints in terms of design space, mobility and cost; and high entry-barriers for developers.

The objective of our research is to lower the barrier for developers to create hybrid games. In [START_REF] Mora | The Interactive-Token Approach to Board Games[END_REF] we proposed the Interactive-Token approach (ITo) to hybrid games. The approach, grounded in Tangible User Interfaces frameworks [START_REF] Ullmer | Token+constraint systems for tangible interaction with digital information[END_REF][START_REF] Ishii | Tangible Bits: Beyond Pixels[END_REF], is based on the concept of tokens, constraints and interaction events. It proposes the design of hybrid games based on interactive game pieces only, without using interactive surfaces. In the approach, the board is preserved as a low-tech component. Because of not relying on interactive surfaces or external sensing infrastructures, ITo provides an extended design space and mobile alternative to interactive tabletops and surfaces.

In this paper we present Anyboard, a platform for creating hybrid board games based on the ITo approach. The platform supports design and prototyping of games. Anyboard design concepts help modelling hybrid game user interaction with technology-augmented game pieces, facilitating the transition between design and implementation. Anyboard software and hardware tools support prototype development with (i) a set of interactive physical game pieces that can be reused across different games, and (ii) a software library to support the coding of games. Our platform aims at reducing the gap between design and prototyping making it easier for designers to use technologies such as sensors and actuators that usually require engineering skills. It should be noted that Anyboard focuses on supporting interaction design rather than more "traditional" game development components such as game engines.

The paper is structured as follows. We first provide a definition of the ITo approach, followed by existing tools for supporting development of hybrid board games. Second we describe the architecture of Anyboard, listing the tools and APIs provided to developers. We evaluate the power of Anyboard illustrating how it could be used to implement common board game mechanics. We conclude highlighting future work.

Hybrid Board Games: The ITo Approach

With the dawn of the ubiquitous computing age, board games gained new interest. Advances in interactive surfaces enabled for the development of hybrid versions of board games with or without augmented playing pieces. For example in [START_REF] Bakker | Weathergods: tangible interaction in a digital tabletop game[END_REF] players use interactive physical iconic or symbolic artifact as their avatars to perform actions in the game. In [START_REF] Leitner | Physical interfaces for tabletop games[END_REF], players can interact on a virtual game board with smart-pens and combine physical and virtual objects to solve puzzle games.

In recent years the large adoption of smartphones and tablets fostered the creation of hybrid games for mobile platforms. To address the limited screen size that impedes co-located play, technologies in the field of Multi-Display Environments (MDE) [START_REF] Mueller | Capture The Flag: Engaging In A Multi-Device Augmented Reality Game[END_REF] and Around the Device Interaction (ADI) [START_REF] Garcia-Sanjuan | Around-Device Interactions: A Usability Study of Frame Markers in Acquisition Tasks[END_REF] were adopted. In hybrid games such as Capture the flag [START_REF] Mueller | Capture The Flag: Engaging In A Multi-Device Augmented Reality Game[END_REF], gesturing and juxtaposition of private smartphone screens onto a shared screen reveal hidden layers and provide player-custom perspectives into the game. ADI technologies have demonstrated the development of augmented game pieces capable to control the behavior of a smartphone game by manipulation over or around the screen. Airsteroids [START_REF] Garcia-Sanjuan | Airsteroids: Re-designing the Arcade Game Using MarkAirs[END_REF], a spaceship game, demonstrates how the game space can extend across several tablets brought in by players and the use of augmented cards to control spaceships' heading.

These examples show how hybrid games usually rely on a mix of private and shared interactive surfaces as a primary mean to convey interactivity, with augmented game pieces as helpers. This approach poses several limitation in terms of mobility and cost and it requires engineering skills to orchestrate the diverse technologies; limiting the adoption of hybrid games outside research labs.

In the ITo approach, game pieces (tokens) with embedded sensors and actuators are the primary means to add interactivity to board games, while the cardboard is preserved as passive. In this way the same tokens can be used to play multiple levels or games just printing a new cardboard with consumer-grade devices. Technology is used to enhance control and representation roles of game pieces. Tokens can control the state of a game by capturing players' interaction events. For example an accelerometer embedded in a dice can sense the result of a dice throw, and notify a computer game engine in a way that is transparent to the player. At the same time, tokens can represent the state of a game by producing digital feedbacks; e.g. via graphics, haptics or sound via embedded displays and actuators.

Distributing interactivity across multiple components opens for a wider space of possibility in designing game experiences. Tokens are active playing pieces and they can influence the state of a game not only when they sit on an interactive surface, but also when they are manipulated over and around it. Finally, because of relying on embedded technology not requiring external hardware, ITo offers a more mobile and cost effective alternative to tabletop and ADI technologies. For more information about the ITo approach see [START_REF] Mora | From interactive surfaces to interactive game pieces in hybrid board games[END_REF].

Challenges to the development of hybrid games

The development of hybrid games based on the ITo approach poses several challenges, mixing issues typical of both board and computer games [START_REF] Lilis | An Integrated Development Framework for Tabletop Computer Games[END_REF]. These challenges are often common to many pervasive [START_REF] Magerkurth | Pervasive games: bringing computer entertainment back to the real world[END_REF] games. From a design point of view there is a lack of theoretical tools to model players' interaction as well as abstractions to describe common elements of games. In particular, the complexity of dealing with different low-level hardware and software technologies, for example to detect manipulation of augmented game pieces, makes game development hard to non-expert, creating a gap between design and prototyping tasks [START_REF] Marco | ToyVision: a toolkit to support the creation of innovative board-games with tangible interaction[END_REF]. Further, besides game pieces and mechanics can be generic, the implementation is often so specific that cannot be re-used to develop similar games [START_REF] Lilis | An Integrated Development Framework for Tabletop Computer Games[END_REF].

Software frameworks and game engines for development of video-games can partially help development, however special tools are often needed to exploit at full the design space. Tangible User Interfaces prototyping toolkits, such as Arduino [START_REF] Mellis | Arduino: An open electronic prototyping platform[END_REF] and Phidgets [START_REF] Greenberg | Collaborative physical user interfaces[END_REF] can be used to implement interactive pieces, although they don't specifically address game development. Conversely, toolkits to support hybrid game development often focus on tabletop or tablet computing platforms; for example supporting object recognition and tracking as for game pieces [START_REF] Dietz | DiamondTouch: a multi-user touch technology[END_REF], dealing with multiple screens [START_REF] Magerkurth | STARS -a ubiquitous computing platform for computer augmented tabletop games[END_REF], designing terrain composition and dealing with input management [START_REF] Lilis | An Integrated Development Framework for Tabletop Computer Games[END_REF], or facilitates the development of games that feature playing pieces on and around a tablet screen [START_REF] Avrahami | Portico: tangible interaction on and around a tablet[END_REF].

Only a few toolkits [START_REF] Marco | ToyVision: a toolkit to support the creation of innovative board-games with tangible interaction[END_REF][START_REF] Krzywinski | RoboTable: a tabletop framework for tangible interaction with robots in a mixed reality[END_REF] explicitly support the development of interactive game pieces required by the ITo approach, and only as complement to tabletop interactive surfaces. An integrated set of design and prototyping tool to support the development of ITo hybrid games could not be found.

The Anyboard platform

Building on analysis of development tools available and our experience in building hybrid games [START_REF] Mora | The Interactive-Token Approach to Board Games[END_REF] we created the Anyboard platform (Figure 1). AnyBoard implements the ITo approach providing:

-Design entities to model interaction styles and provide a common terminology to describe games both in design and implementation phases -Interactive game pieces and cardboard templates to support the construction of the game hardware (Figure 2) -AnyboardJS library to facilitate coding of games by abstracting the complexity of dealing with hardware and low-level programming

Design entities

Design entities derived from the ITo approach [START_REF] Mora | The Interactive-Token Approach to Board Games[END_REF], listed below, constitute the foundation of a language to model interaction styles with Anyboard games. They have been mapped to traditional board games elements in Table 1, to help bridging the gap between game design and development. Tokens are technology-augmented artifacts which resemble traditional game pieces; ranging from elements of chance (e.g. an augmented dice in Backgammon or RFID-enabled cards in Monopoly) to game pieces, e.g. pawns augmented with an LCD displaying the player's rank in the game.

Constraints are either visual or physical confining regions in the board space. The association or dissociation of a token within a constraint can be mapped to digital operations to activate game dynamics. Examples of constraints are checks for Chess pieces and territories in Risk.

Interaction events are player-triggered manipulations of tokens, that modify the (digital and physical) state of a game. We define three types of events:

token event (TE) -the manipulation of a single token on, over around the board; e.g. the action of rolling a dice or drawing a card token-constraint event (TCE) -the operation of building transient tokenconstraint associations by adding or removing tokens to a constrained region of the board; e.g. moving army pieces beyond a territory line as an attack action token-token event (TTE) -the operation of building transient token-token adjacency relationships, achieved by moving tokens on the board; e.g. moving a token next to another token to exchange a resource between two players.

An Anyboard game can be therefore defined as a sequence of player-initiated interaction events that modify spatial configurations of tokens with respect to board constraints and other tokens. As a consequence tokens' intangible (digital feedbacks) representations are updated.

Sequences of interaction events describe players' actions during the game and are mapped to specific game dynamics implemented in a game engine.

The game engine connects and exchange data with tokens using the Any-boardJS library (Section 3.3) running on the user's smartphone, for example activating specific game mechanics according with interaction events sensed by tokens or triggering digital feedbacks.

Design entities have driven the development of hardware and software tools to assist the making of Anyboard games.

Interactive game tokens and cardboard template

Anyboard currently prototypes two different types of interactive tokens: aPiece, an augmented game piece, and aDeck, an augmented card deck (Figure 2). Being two of the most common elements of board game they can be used to implement a wide range of games.

aPieces are a technology-augmented version of game pieces commonly found in most games. They are capable of capturing the set of interaction events and produce digital feedbacks. Table 2 and 3 cluster interaction events and digital feedback supported by typology and provide a player-perspective description of their role. Possible mapping with dynamics commonly found in board games are also exemplified. For example the action of shaking an aPiece can be mapped to the draw of a random number or event.

aPiece has been designed and implemented using custom components. This choice allowed the use of miniaturised components, leading to aPieces with volume and affordances similar to traditional game pieces. aPiece embedds an ARM processor, which runs a custom-designed firmware, and a BTLE (Bluetooth Low Energy) radio transmitter. It implements algorithms to handle sensors data and drive feedback actuators as well as establishing wireless links with the game engine. The core unit is complemented by circuitry for battery charge and firmware upgrade.

TEs (Token Events) are recognised by a 3-axis accelerometer implementing algorithms for extracting features to identify physical manipulation events (e.g. SHAKE, TAP). TCEs recognition is implemented by assigning and imprinting unique colors to different sectors of a game board (representing visual constraints to token's locations). A color-sensor located on the bottom of aPiece samples the color temperature of the surface the device is lying on, returning an unique colorcode which is used as a fingerprint for board constraints, enabling to detect when aPiece is moved between two sectors. TCE detection also makes use of accelerometer data to ensure that color sampling is performed only when the device is steady on a sector, deactivating the sensing routine when aPiece being moved.

TTEs are recognised by computing the distance between two pawns using RSSI (Received Signal Strength) data from the radio transmitter.

Token digital feedbacks are implemented using three different devices: an RGB LED, a 8x8 LED Matrix and a vibration motor.

The aPiece firmware (Figure 1) can be extended using Arduino code. In this way new functions can be added allowing implementing new interaction events and extending the range of feedbacks. Further, the firmware can be used as a template to develop new tokens. The appearance of aPiece can also be customized with handcrafted or 3D-printed models blending the digital feedback with a static iconic or symbolic shape.

aDeck is an interactive version of the card deck commonly found in board games. Instead of holding stacks of cards, aDeck prints out its own cards using a small thermal printer. aDeck provides visual feedbacks as listed in Table 4.

Besides having textual and graphical information on card, aDeck can also be configured to print cards with 2D-barcodes that can be recognised by smartphone cameras or dedicated devices, and used in certain games to trigger game A new card with an graphical icon is printed Represent a resource that the player owns CARD[barcode] A new card with a barcode is printed Trigger an action when barcode is scanned aDeck is implemented using a thermal printer capable to print on conventional thermal paper up to 4.8cm length, and an Arduino-compatible board.

Cardboard templates provide support to creating custom cardboards that interact with iPieces. As mentioned above, Anyboard use color temperature sensing to implement constraint regions.

We therefore selected nine colors that provided satisfactory sensor recognition rate across different materials and printing techniques and associate them with unique IDs to be used in game development. A color palette to draw cardboard with custom constraint regions is provided as a template file that can be modified with vector graphic editors (example in Figure 2).

AnyboardJS

AnyboardJS is a javascript library providing developer-friendly functions to code games (Figure 3). It acts as an interface between the interactive tokens provided by the Anyboard platform and game-specific code developed as standalone or with third-party game engines. AnyboardJS provides two main functions. It establishes wireless links with aPieces and aDeck enabling data exchange using specific drivers for each type of token. It provides a TokenManager interface to enable developers to easily write javascript code to handle interaction events from tokens and generate digital feedbacks, to implement game-specific routines. The library is designed to be extensible, support to new interactive tokens can be added by writing driver modules. Although tokens are the primary user interface with a game, it is possible to code a secondary GUI to display extended information and controls on the smartphone screen; e.g. to be used to edit game settings, to display game rules and leader-boards. This functionality can be implemented with external libraries (e.g. jQuery mobile1 ).

A subset of the TokenManager interface functions is provided in Figure 3. AnyboardJS is built on top of the Apache Cordova framework2 , and it can deployed on a number of mobile platforms. Further the library has been designed to be used with standard javascript code, to implement simple games, but it can also be integrated with third-party game development frameworks such as UnityMobile3 or Phaser4 for building complex games.

Discussion: Making an Anyboard game

Making an hybrid game using Anyboard is a two-steps process. First it requires to model game pieces, rules and mechanics using the provided design entities (Section 3.1). Second it involves prototyping the game using the provided interactive game pieces and the AnyboardJS library. Our platform saves developers from taking care of low-level implementation details, yet leaving freedom for customization.

As a working example, we consider the popular board game mechanic of resource trading, for example transferring the ownership of a property in a game like Monopoly. This mechanic could be implemented in hybrid board games by having two tokens, avatars of players, moved close to each other to symbolize the resource transaction between the two. Digital feedbacks can acknowledge the player with approval or failure (in case of no funds available) with visual or haptic feedbacks.

Implementing such mechanic with current tools would take multiple efforts. First, game designers and developers should agree on common terminology to describe the mechanic and playing pieces involved, because there's usually no such "resource trading" API in game development toolkits. Second, game developers should build the tokens and implement recognition of tokens manipulation and production of digital feedbacks, dealing with diverse hardware and software low-level technologies. Third, the developer should design data transfer protocols and implement interfaces between interactive tokens and game-specific code.

Developing the described mechanic with Anyboard requires only two steps. First, Anyboard design entities offer a choice of opportunities to model the trading mechanic, simplifying transition between game design and implementation. Two aPieces tokens can be used as avatars for the two players, the seller and the buyer. When the two tokens are moved close to each other in a Token-Token Interaction Event, the resource is exchanged among the two player. As a consequence, tokens' feedbacks can acknowledge the player with a graphic representation. Second, using AnyboardJS, the mechanic can be easily translated into code which handles interaction events and triggers feedbacks (Listing 1.1); acting as an interface with digital model of the game implemented in a game engine. This simple example can be further extended to leverage other Anyboard functions. For example, the trading action to be only allowed when both tokens are in a specific constrain sector, detected by a Token-Constraint event. Otherwise aDeck could be used to issue an "ownership certificate" reporting the name of the new owner and current property value.

Anyboard makes it easy for developers to explore design choices just editing a few lines of code. For example, the digital feedback in the example above, provided in a form of iconic visualization can be instead provided with haptic feedbacks or with color codes, using aPiece's LED. Information provided to the player can mix tangible and intangible representations. For example, static information like players identities or roles can be provided by customizing aPieces with 3D-printing and handcrafting work, instead action points or other dynamic information can be provided using digital feedbacks.

Anyboard has been designed to be extensible, experts can create interactive tokens of their own, with different sensors or feedback capabilities, tinkering with the Arduino-compatible firmware developed for aPieces and by writing driver modules for AnyboardJS.

Conclusion and Future Work

The Anyboard platform contributes to hybrid board game research with design and prototyping tools to create games based on the ITo approach. Design entities facilitate modelling game mechanics, while interactive tokens supported by a Javascript library shield developers from dealing with hardware complexities and low-level software development. We expect Anyboard to lower the thresholds of technical competences needed for game development.

Anyboard source code and hardware schematics are open source 5 . Future work will have multiple efforts. On one side we aim at better understanding the expressive power of Anyboard design entities by systematically modelling popular game mechanics, adding to the mapping already provided in Tables 2, 3 and 4. On the other side we plan to run game design workshop to evaluate developer friendliness and performances of the tools. Finally there are also plans to build new type of interactive tokens to further explore the space of opportunities provided by the ITo approach.

Fig. 1 .

 1 Fig. 1. Anyboard platform overview

Fig. 2 .

 2 Fig. 2. Interactive game pieces and carboard template prototype

Fig. 3 .

 3 Fig. 3. AnyboardJS library internals and API

Listing 1 . 1 .

 11 Example of game mechanic implemented with AnyboardJS var t r a d e = f u n c t i o n ( i n i t T o k e n , respToken , o p t i o n s ) { i f ( i n i t T o k e n . f u n d s A v a i l a b l e ( ) ) { t r a n s f e r p r o p e r t y ( ) ; i n i t T o k e n . t r i g g e r (MATRIX, "ICON OK" ) ; respToken . t r i g g e r (MATRIX, "ICON OK" ) ; } } TokenManager . onTokenTokenEvent ( "MOVE NEXT TO" , t r a d e ) ;

Table 1 .

 1 Mapping between Anyboard and board game concepts

	Anyboard design entities Traditional Board Game elements
	Tokens	Game pieces
	Constraints	Board tiles or sockets
	Interaction Events	Player's actions

Table 2 .

 2 Interaction events implemented by aPiece

	Type	Interaction	Description	Sample mapping with game
		Event		mechanics
	TE	SHAKE	aPiece is shaken	Throw a random number
		TILT	aPiece is tilted upside down Undo a previous action
		TAP	aPiece is tapped on the top	Increase a resource by one
			side	unit
		DOUBLE-TAP aPiece is double-tapped on	Decrease a resource by one
			the top side	unit
	TCE	ENTERS [cID] aPiece is moved inside a cID	Signal player's placement
			sector of the board	and movements among
		LEAVES [cID] aPiece is moved away from	different board sectors
			cID sector
	TTE	APCHES [aID2] aPiece is moved close to	Trade a resource between
			another one	two players
		LEAVES [aID2] aPiece is moved away to	Break a relationship between
			another one	two players

Table 3 .

 3 Digital feedbacks implemented by aPiece

	Type	Feedback	Description	Sample mapping with game
		(FEED-		mechanics
		BACKID)
	Visual LED [color]	aPiece lights up in the color	Show the status of a resource
			defined by [color]
		MATRIX [text] aPiece top side display shows	Shows player's action point
			the string [text]	allowance
		MATRIX [icon] aPiece top side display shows	Show the result of a dice roll
			the icon [icon]
	Haptic SHRT HAPTIC aPiece produces a short	Signal a player to move to
			haptic feedback	the next turn
		LNG HATIC	aPiece produces a long	Signal a player an action not
			haptic feedback	allowed

mechanics. This is not yet specifically addressed by our platform but can be easily implemented with third-party tools.

Table 4 .

 4 Digital feedbacks implemented by aDeck

	Type	Feedback	Description	Sample mapping with game
				mechanics
	Visual CARD[text]	A new card with textual	Inform the player about an
			information is printed	event
		CARD[icon]

jQuery mobilehttps://jquerymobile.com/

Adobe Cordovahttps://cordova.apache.org/

UnityMobilehttps://unity3d.com/

Phaserhttp://phaser.io/

Acknowledgements We thank Dr. Ines Di Loreto for her contribution to the ITo approach formalisation and her feedbacks on Anyboard.