<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>Heidelberg, Germany, Online, September</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Secrets of the South: A Location-based Game for the Development of 21st Century Social Skills and Promotion of Social Interaction</article-title>
      </title-group>
      <contrib-group>
        <aff id="aff0">
          <label>0</label>
          <institution>Faculty of Technology</institution>
          ,
          <addr-line>Policy and Management, TU Delft, Delft</addr-line>
          ,
          <country country="NL">Netherlands</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>HIT Lab NZ, University of Canterbury</institution>
          ,
          <addr-line>Christchurch</addr-line>
          ,
          <country country="NZ">New Zealand</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2020</year>
      </pub-date>
      <volume>15</volume>
      <issue>2020</issue>
      <fpage>0000</fpage>
      <lpage>0003</lpage>
      <abstract>
        <p>Location-based games (LBGs) successfully promote playful experiences engaging millions of players throughout the world. The potential of embedding such location-based experiences in educational practice has been recognised but not yet fully embraced. LBGs and educational location-based applications have been used to enhance critical thinking, but not for the acquisition and development of 21st century skills: key competences required to understand, live and thrive in the local communities of today. This paper introduces the LBG 'Secrets of the South', designed to orchestrate social interaction in public space, and foster communication, collaboration, IT literacy, and social/cultural skills through 1) interaction-based social encounters with both friends and unknown members of the community, and 2) in-situ learning about the history and social context of the neighbourhood. A 4-step general procedure is proposed for the creation of LBGs designed to foster 21st century skills.</p>
      </abstract>
      <kwd-group>
        <kwd>Location-based game</kwd>
        <kwd>Social interaction</kwd>
        <kwd>21st century skills development</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>
        Location-based games (LBGs) are a relatively new type of game (since early 2000’s)
that enable innovative forms of play when compared to traditional games [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. Their
ability to blend the fictitious and surrounding real environment of players, together with
their very contradictory gameplay between the crossroads of “fun” and “serious”,
render them a very promising means to approach existing societal challenges in a unique
way [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. LBGs expose players to the real world and invite them to actively engage and
interact with both their surroundings [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Due to these affordances, LBGs have been
explored for the betterment of society [
        <xref ref-type="bibr" rid="ref10 ref11 ref12 ref4 ref5 ref6 ref7 ref8 ref9">4-12</xref>
        ], such as fostering meaningful social
interaction in public space [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ].
      </p>
      <p>
        Meaningful social interaction is argued to be one of the key requirements for social
cohesion and social resilience. Meaningful social interaction has shown to be essential
to break down stereotypes and prejudice, increase people’s ability to act, and address
conflict [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ]. Several LBG-based initiatives have been successful at promoting
community-wide playful behaviour that brings communities together to this purpose [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ].
      </p>
      <p>
        Such interaction requires 21st century skills [
        <xref ref-type="bibr" rid="ref16 ref17">16, 17</xref>
        ]: the social and cultural skills
needed for citizens to understand and grow in today’s ever changing societies [
        <xref ref-type="bibr" rid="ref18 ref19">18, 19</xref>
        ].
These skills include the ability to work with others in multi-cultural environments, to
build and maintain a social network, and to communicate and collaborate with (both
known and unknown) others [
        <xref ref-type="bibr" rid="ref16 ref20">16, 20</xref>
        ]. The importance of critical thinking is well
recognised: 70% of the games developed for educational purposes focus on this skill [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ].
The potential of educational location-based games and applications with high real-life
relevance for other 21st century skills, however, has yet to be successfully embraced in
formal/informal educational settings [
        <xref ref-type="bibr" rid="ref22">22</xref>
        ].
      </p>
      <p>This paper presents an LBG designed to foster social interaction in public space and
played by children, adolescents and adults in their own neighbourhood, and deployed
to this purpose. This LBG supports the development of communication, collaboration,
IT literacy, and other social/cultural skills through 1) interaction-based social
encounters with both friends and unknown members of the community, and 2) in-situ
learning about the history and social context of their local neighbourhood. This paper also
proposes a general procedure to create similar LBGs in the future, a procedure where
future players are invited to be at the centre of the development process and asked to
inform on the gameplay most meaningful to them.</p>
      <p>The next section presents the background on location-based games developed for
social interaction and the development of the 21st century skills. The following sections
present the research context, methodology, game design, and a discussion on the
implications of the design for learning 21st century skills. The last section presents a
conclusion and discusses limitations of the research and directions for future work. A detailed
discussion of the design choices behind the proposed game design based on the
requirements presented in the research context section is included in the appendix.
2</p>
    </sec>
    <sec id="sec-2">
      <title>Background</title>
      <p>
        LBGs are designed for/require players to interact both with their physical
surroundings, as well as socially with people within and outside the game world. They are known
to expand the fictitious boundaries of play that traditional games offer with an
ubiquitous outdoor play experience in an outdoor location (with GPS coverage) with its
specific context (dependent on the availability of network service) [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Such games can
provide powerful forms of entertainment, exposing players to the real world and
inviting them to actively engage and interact with their surroundings [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ]. Pokémon Go is
an example of an LBG [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] that has become so successful that cities have explored its
use for purposes such as boosting civic engagement in local communities, involving up
to thousands of people [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ], and increasing meaningful social interaction in public
space (linked in turn to the strengthening of the social fabric of local communities).
2.1
      </p>
      <sec id="sec-2-1">
        <title>LBG Initiatives for Social Interaction</title>
        <p>
          Examples of commercial LBGs that trigger interaction include Pokémon Go [
          <xref ref-type="bibr" rid="ref24">24</xref>
          ],
Ingress [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ], BotFighters [
          <xref ref-type="bibr" rid="ref6">6</xref>
          ], and Geocaching [
          <xref ref-type="bibr" rid="ref25">25</xref>
          ], all of which motivate players to move
around a physical location, collect items, interact with real objects, and play
individually or in a team of players [
          <xref ref-type="bibr" rid="ref26">26</xref>
          ]. LBGs designed for research purposes such as
Insectopia [
          <xref ref-type="bibr" rid="ref10">10</xref>
          ], Mythical: The Mobile Awakening [
          <xref ref-type="bibr" rid="ref27">27</xref>
          ], Day of the Figurines [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ], and
CityConqueror [
          <xref ref-type="bibr" rid="ref12">12</xref>
          ] are based on similar gameplay, and have been explicitly designed to
explore the impact of various design choices and game features [
          <xref ref-type="bibr" rid="ref28">28</xref>
          ]. Many of these
games have successfully fostered social interaction although it is often unclear why
and how [
          <xref ref-type="bibr" rid="ref26 ref29">26, 29</xref>
          ], as the aims often differ. Most LBGs, both commercial and academic,
are designed and developed without the involvement of users in early stages of game
development for which requirements elicitation is an in-house process, often involving
users in the testing phase. Recent research indicates the need for a better understanding
on how to best design LBGs for meaningful social interaction, and the need to involve
users and their preferences in early-stages of game design [
          <xref ref-type="bibr" rid="ref26 ref29 ref30 ref31 ref32">26, 29-32</xref>
          ].
2.2
        </p>
      </sec>
      <sec id="sec-2-2">
        <title>Educational Game-based Applications for 21st Century Skills</title>
      </sec>
      <sec id="sec-2-3">
        <title>Development</title>
        <p>
          During the 20th century traditional educational systems focused on teaching specific
knowledge that was key to society’s economies [
          <xref ref-type="bibr" rid="ref33">33</xref>
          ]. Current insights support more
competence-based education in which skills and insights needed in today’s society are
key. Although studies differ in the skills distinguished, a number of skills are almost
always named: communication, collaboration, ICT literacy, and social/cultural skills
[
          <xref ref-type="bibr" rid="ref34 ref35">34, 35</xref>
          ].
        </p>
        <p>
          Serious games for learning provide an environment specifically designed to enhance
the acquisition and development of both knowledge and skills that can be tailored to
guarantee a sense of achievement when a task is completed, and evidence shows that
these encourage meta-skills such as critical thinking, argumentation, collaboration, and
decision making [
          <xref ref-type="bibr" rid="ref36 ref37 ref38">36-38</xref>
          ]. As stated above reviews show that 70% of the studies done
on the promotion of the 21st century skills are directed towards critical thinking skills,
and only one study was found with the focus on communication as a learning outcome
[
          <xref ref-type="bibr" rid="ref21">21</xref>
          ]. The scarce research on games for the development of social and cultural skills is
limited to the usage of virtual worlds, where interpersonal competences such as
communication, social and cultural skills are promoted through virtual interaction and
avatars [
          <xref ref-type="bibr" rid="ref34 ref39 ref40 ref41 ref42 ref43">34, 39-43</xref>
          ].
        </p>
        <p>
          This issue is also not currently being addressed in the new trend seen in education:
educational location-based applications (ELAs) [
          <xref ref-type="bibr" rid="ref22 ref44">22, 44</xref>
          ]. ELAs are either applications,
serious location-based games, or commercial LBGs that leverage on the technological
abilities of smartphones to achieve learning outcomes, and have mostly been explored
for environmental education [
          <xref ref-type="bibr" rid="ref44 ref45 ref46 ref47 ref48 ref49 ref50">44-50</xref>
          ]. Researchers have been studying the learning
effect of ELAs and the justification [
          <xref ref-type="bibr" rid="ref51 ref52">51, 52</xref>
          ], but they have failed to address 1) the balance
between complex and simple game designs to fully explore the affordances of LBGs
for learning outcomes all the while lowering technological barriers felt by teachers and
students in the adoption of such tools; and 2) the usage of ELAs specifically for the
development of 21st century skills [
          <xref ref-type="bibr" rid="ref22">22</xref>
          ].
        </p>
        <p>
          On the former point, researchers swing between relatively simple and complex game
designs: more complex designs rely on virtual environments to maximize immersion
and motivation (and report issues such as higher cognitive load) [
          <xref ref-type="bibr" rid="ref45">45</xref>
          ], and relatively
simple designs focus more on engagement levels, but are not technologically ambitious
and thus fail to fully explore the possibilities ELAs afford [
          <xref ref-type="bibr" rid="ref34 ref53">34, 53</xref>
          ]. On the later point,
researchers have focussed on both specific game characteristics (such as augmented
reality and storytelling) and gameplay outcomes (e.g. immersion, engagement) and not
on acquisition of 21st century skills [
          <xref ref-type="bibr" rid="ref44 ref54 ref55">44, 54, 55</xref>
          ]. This means that location-based games
and applications are not focusing on the 21st century skills, are either too complex to be
adopted or too simple to provide substantial added value, and thus fall short on the
positive impact they can have on societies.
        </p>
        <p>This paper argues that LBGs for acquisition and development of 21st century skills
require a balanced game design, one that is capable of exploring the affordances of
LBGs for effective learning outcomes, and with a low technical barrier to be set and
maintained by teachers and students.
3</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>Research Context</title>
      <p>The research on which this paper reports has been performed in the context of a larger
programme on the design of meaningful social interaction in public space through
LBGs in the Hague and in Rotterdam in the Netherlands. This programme included
understanding the need to positively impact social cohesion and social resilience in
local communities. To such end, this research contacted the municipality, the Police, a
cultural Thinktank, and three schools (two secondary, one basic) in Rotterdam, NL, and
a community centre in The Hague, NL, to better understand the social environment and
the preferences and needs of local communities. On the one hand, the non-educational
actors involved (municipality, police, cultural Thinktank, and community centre)
argued that a positive approach (such as games) could be beneficial to some of the local
issues (e.g. related to safety, or lack of neighbourhood engagement). On the other hand,
schools in Rotterdam were particularly engaged with projects that could be adapted to
their existent curricula and that could help promote 21st century skills such as IT literacy
and contextual-based learning. They argue that local communities surrounding their
schools are rich in historical legacy, and that enabling a way for their pupils to be
exposed to it in a fun and engaging way would promote their education.</p>
      <p>
        In such exploration, this research learned that social interaction is a key requirement
for the promotion of social cohesion [
        <xref ref-type="bibr" rid="ref56">56</xref>
        ]. Such social interaction mandates 21st century
social and cultural skills. From this requirement (the central requirement in Fig. 1),
followed the exploration of LBGs with players engaging 1) within their own
neighbourhood, and 2) in meaningful interaction with friends and passers-by. To this
purpose, 4 characteristics were identified for the targeted type of gameplay: an LBG that
1) is played with the smartphone, is 2) fun to play, and that 3) involves known and
unknown people 4) in the neighbourhood of the player (marked as a 2nd ring on Fig. 1).
The game design presented in this paper is a product of an iterative design approach
[
        <xref ref-type="bibr" rid="ref57">57</xref>
        ]. Research in game design argues that an interactive system requires an iterative
design approach with iterations of requirements and (partial) design
artefacts/prototypes [
        <xref ref-type="bibr" rid="ref58 ref59 ref60">58-60</xref>
        ]. The specific stages of an iterative approach named in the literature vary
[
        <xref ref-type="bibr" rid="ref61 ref62 ref63">61-63</xref>
        ], but all describe a stage in which an artefact is firstly designed, then prototyped,
and evaluated/validated1,2,3. These 3 steps can be repeated a number of times, until the
product meets the designers’ goals/mission and system requirements, as depicted in
Fig. 2 (with more detail in the Appendix).
      </p>
      <p>
        The design process for the LBG on which this paper reports took close to two years in
duration, and had the following structure:
1. Requirements elicitation from adolescents, in case study 1 in educational
settings (schools of Rotterdams Vakcollege de Hef, and Scheepvaart en Transport
College, Rotterdam, NL) [
        <xref ref-type="bibr" rid="ref29">29</xref>
        ].
2. Research on requirements for a systems’ architecture for LBGs for social
interaction [
        <xref ref-type="bibr" rid="ref64">64</xref>
        ].
3. Design: conceptualization of initial game design.
4. Development of the first game prototype.
5. Evaluation of first prototype in case study 2 with adults in an informal setting.
      </p>
      <p>
        Feedback of participants was collected to inform further design and
development [
        <xref ref-type="bibr" rid="ref31">31</xref>
        ].
6. Redesign of the prototype for case study 3: Analysis of required functionality,
and learnings from previous steps are used to improve the game prototype.
7. Development of the second version of the game prototype.
8. Evaluation of the second version of the game prototype as case study 3 with
adults in an informal setting [
        <xref ref-type="bibr" rid="ref30">30</xref>
        ].
9. Co-design of gaming activities as case study 4 with children in an educational
setting (school Christelijke Basisschool De Akker). Outcome is a list of
specific challenges (i.e. specific activities, with specific locations in the
neighbourhood), to be adapted to the game prototype as content.
10. Development of 3rd and final version of game prototype, with the defined
game content from previous step, and more intuitive interface.
11. Evaluation of 3rd and final version of the game prototype with children in an
educational setting (same of step 9) [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ].
      </p>
      <p>
        The products of these stages, organised around the adopted iterative design
methodology, are 1) insights on the potential of LBGs for acquisition of 21st century skills, 2)
a 4-step general procedure to create LBGs for meaningful social interaction in public
space, where 21st century skills are acquired/developed (section 4), and 3) the game
design of a fully open-source LBG prototype for the identified purpose, ‘Secrets of the
South’ (SotS) (section 5). Further details on the intermediary case studies can be found
in [
        <xref ref-type="bibr" rid="ref13 ref29 ref30 ref31">13, 29-31</xref>
        ], and lessons learned are summarized next.
4
      </p>
    </sec>
    <sec id="sec-4">
      <title>4 Steps to Build LBGs for Meaningful Social Interaction in</title>
    </sec>
    <sec id="sec-5">
      <title>Public Space</title>
      <p>Given that the social interaction sought is one that bears meaning to players, this
research studied how to design LBGs for such purpose both from the technical
perspective and user perspective. From the research methodology described above, 4 steps are
recommended as general procedure to design and build an LBG capable of inviting and
sustaining social interaction in public space that appeals to players:



</p>
      <p>Step 1. Discovering a set of game dynamics in which players are interested.
Step 2. Distinguishing types of activities, that a game of this type should be
able to offer to children, adolescents and adults.</p>
      <p>Step 3. Developing ideas for challenges by potential players involving the
activities distinguished in step 2.</p>
      <p>Step 4. Identifying the architectural components that are key for such type of
games to work.</p>
      <p>These 4 steps were taken by this research to create the ‘Secrets of the South’ (see section
5), which produced key information concerning the preferences and needs of both
adolescents and adults for the type of interaction and social exposure they want to
experience. These lessons learned are detailed below, and treated as requirements for the
LBG presented in this article:</p>
      <p>
        Step 1 - For the involved players and social context considered, the desired set of
game dynamics are: achievement, real-world play, reinforcement, social interaction,
collaboration, digital interaction, ownership, winning condition, collection, exertion,
virtual representation, mission, community contribution, and lottery. These dynamics
relate to the design of the game world (i.e., the digital game), and are considered to be
high-level requirements regarding the functionality of the game: they guide the choice
and arrangement of game elements and mechanisms to provide the runtime dynamics
of play desired by players (organized in the upper left quadrant in Fig. 3) [
        <xref ref-type="bibr" rid="ref26 ref29">26, 29</xref>
        ].
      </p>
      <p>
        Step 2 - For the reported goal and setup, 7 types of activities are distinguished:
activities that require players to do physical activities (Athlete), find information and
factual knowledge (Detective), explore their neighbourhood (Explorer), propose ideas
and explore opportunities (Inventor), find specific things or people (Hunter), create
and express thoughts, feelings, interests in some form (Artist), and contribute to the
environment and help others [
        <xref ref-type="bibr" rid="ref30 ref31">30, 31</xref>
        ] (Volunteer) - upper right quadrant in Fig. 3.
      </p>
      <p>Step 3 - For the studied neighbourhoods in Rotterdam, 56 game ideas were devised,
indicating the types of activities that appeal to potential players (see bottom right
quadrant in Fig. 3).</p>
      <p>
        Step 4 - For social interaction in public space via LBGs, essential architectural
components are [
        <xref ref-type="bibr" rid="ref64">64</xref>
        ]: Augmentation, Navigation, Interaction, State Progression,
Participation, and Administration. These components, offered in a modular software
architecture, provide the functionality needed to represent the environment of players,
locate them, facilitate interaction with other players/environment/physical objects,
track the gameplay state, enable long-term play for players through
contributions/participation, and manage the game (see bottom left quadrant in Fig. 3).
5
      </p>
      <p>Game Design: Secrets of the South
‘Secrets of the South’4,5 is a location-based game that invites players to discover and
solve challenges (outdoor activities) designed for social interaction. Challenges are
linked to specific real locations, and require players to walk to these locations to find
them. These challenges require players to play together with their friends in
collaboration and competition, involve unknown people nearby in the gameplay, and explore the
outdoor public places around them while looking for clues to solve the challenges (Fig.
4).</p>
      <p>SotS is designed to invite players both in the real world (e.g. with physical contact
and/or face-to-face communication) and the virtual (e.g. through the discovery of
QRenhanced real objects with messages left by other players). These challenges provide
players with opportunities to encounter and engage with other people in their
surroundings, and are strategically located to expose players to both places and local activities
that are not often noticed in the neighbourhood (e.g. local heroes, or the most important
landmark in the country). Each player has an identity QR code that can be scanned for
points and for counting real-world interactions/friendships. Progress in the game is
measured through the friendship points players have, and the number of challenges
solved. The SotS augments players’ awareness of their surroundings through the digital
3D representation of the player (a genderless rabbit), the location where players are on
the map (e.g. the street, a park), and the surrounding infrastructure (e.g. apartments)
Fig. 4.b and c. Throughout gameplay, players can select nearby challenges and tap to
find their location, revealing an animated 3D compass that points to the location to
which players should walk. The challenges that players need to find are also represented
3D on a map, and once players are close enough (50 metres within range), the
information of the challenge and the to-do task can be revealed (Fig. 4.d).</p>
      <p>
        a)
b)
c)
d)
4 http://secretsofthesouth.tbm.tudelft.nl/, Secrets of the South, last visited on 19th Aug. 2020.
5 https://github.com/xavierfonsecaphd/SecretsOfTheSouth, Secrets of the South source code, last visited on
19th Aug. 2020.
Fig. 4. In Secrets of the South, challenges allow players to encounter people or locations that
otherwise stay unnoticed [
        <xref ref-type="bibr" rid="ref30">30</xref>
        ].
5.1
      </p>
      <sec id="sec-5-1">
        <title>Functional Challenge Types</title>
        <p>The different activities proposed by the game require different functionalities from the
game. 6 functionalities are provided: Quiz, Multiplayer, Timed Task, Hunter, Open
Quiz, and Voting. A Quiz presents a closed question (e.g. “How many guards …”) with
a closed answer (e.g. “3”). A Multiplayer challenge facilitates team-based offline
activities (e.g. tick tack toe), and requires an external facilitator to evaluate correctness.
A Timed challenge specifies a specific time frame (e.g. “Find 5 non-Dutch people
within 3 minutes”) - Fig. 5.d. A Hunter challenge presents closed quests (similar to
Quiz), with clues on how to find the person/object sought, requiring a specific QR code
to be scanned as proof of success, supported by additional information (text or images)
on the neighbourhood (Fig. 5.a). An Open Quiz challenge presents players with open
questions (e.g. “How do you feel about …”), to be explored and answered (and are not
further evaluated) (Fig. 5.b). Finally, a Voting challenge invites players to take a picture
of something in the neighbourhood as an answer to a quest and upload it to the game
(with no further evaluation) after which they can vote for solutions given by other
players, thus enabling digital interaction Fig. 5.c.</p>
        <p>a)
b)
c)
d)</p>
        <p>Most types of challenges are marked as solved by the game, right after the player
answers a question, finds a QR code, or uploads an image, and points assigned: 5 points
for incorrect or almost correct answers, 10 points otherwise. Multiplayer challenges are
an exception as they require players to perform activities that cannot be automatically
validated by the game. To have access to this type of challenge, players must form a
team first by scanning each other’s QR IDs. Registered game facilitators with evaluator
rights need to be located in the premises of such Multiplayer challenges (Fig. 6.b), to
rate a team’s performance and mark the challenge as solved. SotS distinguishes 3 types
of player accounts: player, evaluator, and administrator. Dynamic change of roles
during gameplay is supported (Fig. 6.a).
5.2</p>
      </sec>
      <sec id="sec-5-2">
        <title>Participatory System</title>
        <p>
          Fostering player participation during the gameplay is known to fuel longer-term
gameplay, as it tailors the game around the fun and playful behaviour players like most [
          <xref ref-type="bibr" rid="ref65">65</xref>
          ].
As gameplay in SotS is designed for social interaction longer-term gameplay is a goal.
SotS has been designed to support players in creating their own challenges. These
challenges are necessarily linked to specific locations, specifying activities appropriate
to the context of the neighbourhood and the game mission.
        </p>
        <p>Central to SotS is an online information system that contains games and their
challenges. This system is managed by an administrator, whom can create new accounts for
players (described here5). Players in turn, or the administrator, can then log into the
system and access the list of challenges available throughout the world (Fig. 7).
A player can create a challenge of one of the 6 types described above specifying the
specific information required (name, description, location, picture of the challenge to
appear on the mobile game, the task required, and possible answer – depending on the
type of challenge involved). Upon completion the administrator (automatically)
receives a request to verify the correctness and ethics of the challenge (e.g. foul language
should be avoided), and whether it can be made available to others (or not). This is a
security measure that is of specific importance for educational environments (e.g.
younger adolescents). The system presents a map on which players can click to locate
challenges, their type/name, and edit their own challenges. A reserved area is also
available to administrators for system management.
6</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>Discussion: Secrets of the South and the 21st Century Skills</title>
      <p>
        SotS game has been designed to support social interaction in socially challenged
neighbourhoods in Rotterdam and the Hague, tested and evaluated within educational
settings mandating development of 21st century skills [
        <xref ref-type="bibr" rid="ref34 ref35 ref66 ref67 ref68">34, 35, 66-68</xref>
        ], specifically:
communication, collaboration, IT literacy, and social/cultural skills.
      </p>
      <p>
        Communication. This skill plays a central role in many forms of interaction. Verbal
communication is a direct way of interacting: the exchange of language and symbols
(symbolic communication) mediates face-to-face and digital interactions [
        <xref ref-type="bibr" rid="ref69 ref70 ref71">69-71</xref>
        ].
Interacting socially stimulates effective communication, because it puts communication
into practice [
        <xref ref-type="bibr" rid="ref66">66</xref>
        ]. SotS promotes both digital and face-to-face communication. Digital
communication is needed when players scan each other’s QR codes to count
“friendships” made and to form teams, when players vote for each other’s pictures, and when
QR codes are placed in an environment for players to leave texts and images for other
players to find. Face-to-face encounters are promoted in all of the gaming activities
designed for players to play together (e.g. multiplayer challenges) and work together.
Collaboration. SotS offers functionality that promotes collaboration (e.g. team
formation) and competition leading to in-group collaboration (e.g. solving the most
challenges as a team, and be seen in the team leader board). It mediates team formation,
invites players to take on different roles in the team, and enables joint coordination and
performance [
        <xref ref-type="bibr" rid="ref66 ref72">66, 72</xref>
        ]. Challenges designed to promote collaboration designed by
school participants included jointly coming up with a rap song, coordinating athletic
parkour performance with others, and brainstorming about new names for a street.
IT Literacy. The game layout of SotS exposes players to 3 possible languages (English,
Dutch, and Portuguese), and provides an authoring tool for participants to add new
game content (challenges) in any of these (or other) languages. ICT literacy required
for the visualization, understanding and manipulation of game elements [
        <xref ref-type="bibr" rid="ref67 ref73 ref74">67, 73, 74</xref>
        ] is
also implemented in SotS, as it requires the understanding of how to navigate a digital
map and 3D compass to reach the challenges, which was a challenge for younger
players [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ]. The SotS mobile application also requires the navigability throughout the
menus of the game for everything (e.g. avatar exchange, QR code scanning, and leader
board viewing), which players have to learn.
      </p>
      <p>Social/cultural skills. SotS purposefully facilitates the development of social and
cultural skills throughout the game. On the one hand, it offers in-situ learning about the
history and social context of local communities, by promoting a gameplay experience
that exposes players to the social and cultural environment of the neighbourhood.
Challenges invite the discovery of local history and facts that may not be common
knowledge to residents, while exposing players to the social context of the community.
This in turn makes players aware of who is living in the neighbourhood, and exposes
them to any diversity (e.g. ethnicity, languages spoken, and social behaviour). On the
other hand, social and cultural skills are acquired and developed in the SotS through
direct interactions and social encounters. These occur with both friends and unknown
people, as the SotS is developed to involve others in the gameplay.
7</p>
    </sec>
    <sec id="sec-7">
      <title>Conclusion</title>
      <p>This paper explores the potential of an LBG to foster 21st century skills and its design,
and proposes a 4-step general procedure with which future similar LBGs can be created.
Based on the interaction preferences, needs and desires of children, adolescents and
adults, the game design fosters social interaction through gaming activities that
mandate development of 21st century skills (specifically, communication, collaboration, IT
literacy, and social/cultural skills). SotS is a product of an iterative design approach
where player/learner requirements were repeatedly elicited, and where all initial
requirements, constraints, and player/learner requirements were taken into account to
produce a game capable of facilitating meaningful social interaction for which 21st century
skills were vital. 3 case studies were done to validate the triggered social interaction:
the SotS has been developed and tested with children, adolescents and adults in The
Hague and Rotterdam, the Netherlands, where it was shown to successfully foster social
interaction. They followed the proposed 4-step general procedure, where future players
are put in the centre of the game development and asked: 1) the set of game dynamics
that appeal to them most; 2) the types of activities that the aimed LBG should ideally
offer them; and 3) specific game ideas to introduce as game content on their own
neighbourhood. Parallel to these steps was the identification of the technical requirements
(such as architectural components) that this type of games mandate.</p>
      <p>LBGs such as SotS can be used to develop 21st century social skills needed for social
interaction in both formal and informal educational settings. Players of the SotS are
exposed to a gameplay that invites skills such as communication and collaboration to
solve challenges, skills such as IT literacy to navigate through the bend of real and
fictitious game LBGs offer, and social skills required to involve others in the gameplay
and be physically exposed to the neighbourhood. The SotS can be used by players
alone, or by players and teachers for an integration in existent curricula aiming for
contextual learning and 21st century skills development. The proposed LBG requires an
initial setup, after which it can be operated by teachers and non-technical professionals
with a low-maintenance effort.</p>
      <p>With this being said, SotS requires further evaluation to more strongly measure its
impact in different target groups, and within the same target groups in other social
contexts. It was also developed within the greater aim to promote positive social impact
and neighbourhood pride. Informal educational settings can benefit from SotS, as the
game promotes the completion of co-located ludic activities, which in themselves may
promote higher engagement levels when compared to traditional educational settings.
Further studies should assess 1) how engagement changes in learning outcomes related
to the history and social context of local communities with and without the SotS, and
across formal and informal educational settings; 2) how the SotS can be integrated with
broader curricula for the maximization of learning outcomes; and 3) the extent to which
the SotS develops these and other 21st century skills can be measured.</p>
    </sec>
    <sec id="sec-8">
      <title>Supplement: Discussion of Design Choices</title>
      <p>
        The design choices taken throughout the implementation of the game are influenced by
the findings of the studies reported in the methodology section, which had direct
influence in 1) the functionality developed to support the game, 2) the game world, 3) the
content designed for the game, and 4) the system components required by the ‘Secrets
of the South’ to successfully support the designed game play. These design choices are
further detailed in the following subsections.
As shown in Fig. 3, the initial requirement is the development of a game that can trigger
social interaction, and do so while exposing people to the neighbourhood, mandating
the development of 21st century social skills. This lead to the selection of the game
genre location-based games: digital games that use mobile technology with sensors and
wireless connectivity to provide a pervasive game experience. Still, to bring people to
the street and interact, this research programme set 4 constraints based on the lessons
learned from [
        <xref ref-type="bibr" rid="ref26 ref29 ref30 ref31">26, 29-31</xref>
        ]. These constraints stem from the background check on
existent location-based games that are capable of triggering dynamics of play that invite
citizens to engage with their surrounding environment and have social play. These
studies show that fun is a strong factor making people engage in play, which, when
leveraged with the already ubiquitous presence of the smartphone, provide inclusive and
pervasive gaming experiences that are enjoyed by players around the world. The
affordances from these LBGs represent a means to bring people to the street and
potentially engage in interaction, and justify the design choices of this research of using
LBGs with smartphones in the public space of local communities.
8.2
      </p>
      <sec id="sec-8-1">
        <title>Implementation of Functional Types of Challenges</title>
        <p>
          Several of the lessons learned from [
          <xref ref-type="bibr" rid="ref26 ref29 ref30 ref31">26, 29-31</xref>
          ] influenced the choices of which
functionality the game SotS should have. Knowing the types of activities that participants
want to play (from the framework of activity types), and having a pool of specific game
ideas to adapt to the game, such information led to the implementation of what it is
referred in this article as functional types of challenges: challenges offered by the SotS
for players to solve and that are based on specific functionality asked by players. The
functional types of challenges (Quiz, Multiplayer, Timed Task, Hunter, Open Quiz, and
Voting) are implemented based on the framework of activities and the specific game
ideas potential players gave, which shed light on the functionality that the game should
have to support a specific idea. The functionalities required, and design decisions made
to implement them, are justified per functional type of challenge:
Quiz Challenges. The Quiz challenge is materialized from the Detective type of
activity, and the ideas fitting this type. Participants mentioned wanting to ask specific
questions (e.g. “How long does the school exist? Ask somebody for the answer”), and this
requires the implementation of a mechanism capable of prompting players with a closed
question, providing a way for players to introduce an answer, and validate if such
answer is correct or not. This also justifies the decision of implementing a reward system
based on whether the answers given by players are correct or not, to inform players on
the quality of their answer. Another decision made in the implementation of the Quiz
challenge is the ability for players to re-take a quiz challenge that they failed to answer
in a right way. In such case, the challenge is not marked as solved. With regard to the
point attribution, it was decided to attribute points for the correct answer, and count the
quantity of challenges successfully solved (see Fig. 8). Lastly, based on collected
feedback from one of the case studies done, players revealed that not getting an answer right
did affect their engagement in the game. As such, a design choice was made to still
attribute a half amount of points per wrong answer. This can lead players to attempt to
cheat the system by keep introducing wrong answers, but given the purpose of the SotS
(social interaction in public space, through a fun-based gameplay), this is not a problem.
        </p>
        <p>Multiplayer Challenges: Participants were clear with regard to wanting to perform
physical activities, which led to the type of activity Athlete. This specific type of activity
(e.g. doing parkours, communicating without talking, or run with the metro) is difficult
to convert into a digital activity that can be tracked purely with the smartphone (like
the Quiz challenge). Not all activities can be tracked with GPS (e.g. going from point
A to B), and might be solved between multiple players simultaneously (making
validation even harder). Even some activities of the type Artist require the performance to be
observed (e.g. to create music), and require a mechanism of marking these challenges
as completed that is different from pure validation of text.</p>
        <p>As such, the first 2 design choices for this challenge are the request to have players
perform a task (instead of giving an answer - Fig. 9.b), and the need for them to form a
team to do this task or performance. Justifying this is the fact that the ideas given by
participants involve a joint performance (e.g. race against one another), which makes
these challenges inherently multiplayer. Players can create a team by giving a name to
it, and the game suggests a random avatar for the team. Then, the player creating the
team is shown a team QR code, which can then be scanned by other players to join that
team (a player can only be part of one team).</p>
        <p>a)
b)
c)
d)
Fig. 9. Design choices with the Multiplayer challenges (a – team creation, b – the task window
players see in multiplayer, c – user permissions, and d – rating of a team’s performance).
Another design choice in this type of functional challenge was to not validate the
performance of players in their account, but to set up external validators (workshop
facilitators with a player account) by the location where such performances had to be done
by players. This meant the implementation of user accounts with different levels of
access (regular player, evaluator, and administrator), and the creation of a way for
players acting as evaluators to rate a performance. When a team of players finishes the
required performance, one member of the team shows the team QR code to the person
evaluating the performance, and h/she assesses the team’s performance with 3 criteria:
fun, participation, and collaboration. The rating given on each of the criteria (from 1 to
5 stars) is then used to calculate one overall score to be added to all the elements of that
team, plus one challenge completed. The criteria used for validation is a subjective
method dependent on the perspective of the evaluator, but it is not meant to be more
meaningful than adding a way to validate the completion of these challenges and
differentiating the performance of each team for ranking purposes. The role of the
administrator was added to the game in order to allow for a dynamic attribution and removal
of the evaluator roles to/from different players, during the game play: the administrator
does this management of attributions. Both the roles of evaluator and administrator
have access to more menu options than what it is shown to the role of regular player.
Timed Task. Some of the challenges participants provided that are specific to the type
Athlete require tracking time. Ideas such as “how long does it take to…”, “find within
one minute 10 people that …”, “how many … can you make within 1 minute”, and “be
the fastest at…”, all require two specific functionality to be developed: 1) the
countdown of a predefined amount of time, and 2) the tracking of how much did the player
do or collect. Therefore, these ideas require more functionality that is not provided by
the previous two challenge types Quiz and Multiplayer. A Timed Task challenge is
created in the game: this is a challenge that can be done by one player (no need for a team),
that invites players to do a task within a given amount of time. When players encounter
this type of challenge on the map, a window is offered where they can read the question,
and another that offers a way to start the timing whenever players are ready to start the
countdown. During this countdown, players can cancel the countdown, click to stop the
countdown and introduce their input, or simply let the countdown finish. As the next
step (the tracking of how much did the player do or collect), the game offers a way for
players to introduce a number. The design choice taken here is that the game does not
offer a mechanism of validation, and just accepts a number with a quantity of how many
“things” players did/collected. The reason for this is that offering a more meaningful
validation would require a much more complex process of double checking whether the
payer actually performed, which would hardly be solved with one external facilitator
alone.</p>
        <p>a)
b)
c)
d)
Fig. 10. Design choices with the Timed Task challenges (a – main window inviting for the task,
b – window initiating the challenge, c – timer countdown, and d – the how many question at the
end of the challenge).</p>
        <p>When the player finishes the Timed Task, h/she gets a predefined number of points (e.g.
10 points), that are then added the number of things the player did/collected in addition.
As an example, if the task were for the player to convince at least 5 people within 2
minutes to use the bicycle instead of the car, and if the player upon completion
introduced 7 people, h/she will get 17 points. This design choice for this type of functional
challenge makes the game blindly trust the honesty of players, which of course can
invite dishonest play. Still, as the purpose of the game is for players to have fun while
being invited to have nice interactions throughout the neighbourhood, that potential
foreseen consequence is not substantially harmful to the gameplay.</p>
        <p>Hunter Challenges. The type of activities Hunter from the topology translated to new
functionality in a straightforward way, leading to this type of challenge. The ideas
participants gave that fit into this type require players to 1) find specific objects in the
environment (e.g. a specific flag, or a tile on a wall), and to 2) learn more about that
object (e.g. which flag hangs here, or the biography of a soccer player whose name is
engraved on a tile). As such, this type of activity requires players to ask around for
information concerning the meaning of a given object/topic, which led to the first
design choice of validating this type of challenge in the same way as Quiz (the
introduction of an answer to a closed question). A second design choice was the usage of QR
codes so that players can figure out about a given object in case no one is around to find
the required information.</p>
        <p>a)
b)
c)
d)
Fig. 11. Design choices with the Hunter challenges (a and b – activation of QR reader from main
menu, c – text message from a specific Hunter challenge QR code (schools in the
neighbourhood), and d – message of recognition that a QR code of this type of challenge was
found).</p>
        <p>These design choices are justified because one of the ideas were converted in a case
study to find out more information about what is done at a specific community centre
of the neighbourhood: in this idea, players should find out about the agenda offered by
this centre, and answer a specific question of “what happens at 8 p.m. on Fridays?”.
The answer (e.g. game night), which is given by a person working at this centre, might
not be possible to get at all times. This led to the creation of QR codes that can be glued
to the door of the community centre, and can trigger the game to show the entire agenda
for players to seek the correct answer. This motivated the implementation of the display
of either text or image to be shown while scanning the QR code attached to an object,
and, as the objective here is to expose players to the neighbourhood, the Hunter
challenge gets solved when 1) players spoke to a person and introduced the correct answer,
or 2) when they simply scan the QR code (without further validation). This means that
the main dynamic of solving Hunter challenges is the one of finding a specific person
that can help the player out, and this is what is shown to players in the challenge window
that pops up in the main screen (the possibility to introduce the correct answer to the
challenge, identical to what is shown for the Quiz challenges in Fig. 8). On top of this,
Hunter challenges can also be solved by finding a QR code, which is scanned through
using the QR reader from the main drop down menu. The implemented flow of solving
this type of challenge (Fig. 11) is chosen to be integrated with the already existent QR
Reader for all other types of QR codes offered within SotS (e.g. Player ID, and Team
ID). With these design choices, players can play the ideas where they solve challenges
by finding a specific object, all the while learning more about the neighbourhood even
when no one is around to communicate such information in person. They also allow for
players to inquire passers-by in the neighbourhood about important objects spread
across the neighbourhood (e.g. “ask people to come up with 3 names of soccer players
from the neighbourhood and find their tiles”), which in turn can be found and marked
as solved around the clock.</p>
        <p>Fig. 12. Design choices with the Open Quiz challenges.</p>
        <p>Open Quiz Challenges. Several ideas of activities from the participants fitting the
types Artist and Explorer indicate that new functionality needed to be developed in
order to capture the thoughts of players in an open way. So far, challenge types like
Quiz and Hunter ask closed questions of players, and these, in turn, have to introduce a
very short and specific answer to be validated. Yet, participants mentioned challenges
such as “write a poem about the neighbourhood”, “come up with ideas for new street
names”, “for what is … used”, which all of them invite open answers (i.e. have a
varying length and no specific answer). As such, these ideas required the development of
new functionality that allowed players to introduce any sort of text content into a
challenge, and mark this challenge as completed as soon as that content is put into the game
(with no further validation). This led to the design choices of creating a new functional
type of challenge (named Open Quiz), the display of a full screen answering box (Fig.
12), the marking of the challenge as solved as soon as the player introduces his/her
answer, and, given that it is likely that the information is valuable and should be
collected for future analysis, the answers given are stored in a database and sent via email
to the administrator of the SotS game (in case further analysis of the game play, during
play or after, is desired).</p>
        <p>Voting Challenges. The specific ideas from the participants fitting the activity types of
Artist, Inventor, and Volunteer required new functionality not implemented with the
other functional types of challenges. In specific, ideas such as “make a picture”, “come
up with a colour scheme for the square”, “painting”, and “make a plan to …” all require
the ability to either take a picture of something that players find interesting, or to
document a creativity-based artefact (e.g. drawing, painting, sketch, or schema). In a few
of the ideas of the Volunteer type it is also possible to see the usefulness of being able
to document the performance of players in, for e.g., picking up trash, or carrying
someone else’s bag. Thus, these requirements led to the design choices of implementing a
new type of challenge (Voting), which prompts players to do something, take a picture
of it (or simply take a picture of something already existent), give a name they want to
attach publicly to the picture (can be theirs, can be anything they want), and upload it
into the game. The design choice of allowing players to attach any name they want to
the picture is to allow the participation of players that rather prefer having their
identity/name kept private. Pictures uploaded into the game are attached to that specific
challenge as a solution, and players get the challenge marked as solved once they
submit a picture as the answer (which, similarly to the other challenges, gives points to
players). Only when a Voting challenge is marked as solved (by having the player
submitting a picture) can the player see all the pictures that other players submitted to that
challenge in particular. Given that this is a location-based game, this detail also
motivated the design decision to only show the solutions of that challenge when the player
is co-located to the challenge.</p>
        <p>When players submit their solution to the challenge and are then able to see the
solutions of other players, they can browse these pictures, see the names of their authors,
and vote for them (not for their own picture). The voting mechanism is a design choice
motivated by some of the ideas that are either competitive in nature (e.g. “the person
who collects the most litter wins”), or promote the ideation of an improvement for the
neighbourhood (e.g. “increase attractiveness of the location by …”) which, in the
future, can actually inform policy makers on how much players liked a given idea. It was
not implemented any point attribution for giving a vote.
Fig. 13. Design choices with the Voting challenges (a – functionality of taking a picture, b –
solutions given by all the players to this challenge, c – the details and votes of one picture, and d
– voting for a picture).
8.3</p>
      </sec>
      <sec id="sec-8-2">
        <title>Implementation of Gameplay Requirements</title>
        <p>
          The list of 14 game dynamics taken by this research as gameplay requirements
(Achievement, Real-World Play, Reinforcement, Social Interaction, Collaboration,
Digital Interaction, Ownership, Winning Condition, Collection, Exertion, Virtual
Representation, Mission, Community Contribution, and Lottery) is a sorted list for game
designers and developers. It is a list that involves substantial implementation and
careful planning during the design of a game, that, depending on the time and effort
involved, might not be possible to be implemented entirely or coherently within one game
idea. As a game developed throughout the better part of 2 years, SotS contains design
choices that implement all of the 14 dynamics, and these are explained below (sorted
by order of importance, first being the most important to participants – see [
          <xref ref-type="bibr" rid="ref26">26</xref>
          ]):


        </p>
        <p>Achievement: SotS aims at providing a sense of achievement by offering small
challenges that can be quickly accomplished. When players solve a challenge,
the game displays a message of “Congratulations, you just solved a …
challenge. Well done.”, and get attributed points even when they introduce a
completely wrong answer to a closed question (in such case, half the points, for
the recognition of the player’s attempt).</p>
        <p>Real-World Play: The entire SotS game is designed to be implemented in the
public space of the neighbourhood of the player, as the GPS being a
technology used that sets a constraint in itself (does not work indoors). This, together
with the fact that each challenge offered by the game is designed to be played
around the neighbourhood, invite a game play centred in the real world. In
addition most types of challenges really stress the physical activity
component, without which players cannot find the answers or complete challenges.
Reinforcement: SotS aims at fostering play and engagement by implementing
the attribution of badges, points and gold, associated with 1) successful
completion of challenges, 2) how many people the player met (by scanning other
players’ ID QR codes), and 3) the creation of challenges for other players to
solve. A few of the statistics of each player change the player’s icon (badge)
based on how high their numbers are: for e.g., the number of people met (Fig.
8, right) changes from a normal smile to a wider smile based on how many
people the player crossed paths with (and scanned the QR code).</p>
        <p>Social Interaction: The challenges currently provided by the game are
designed for the involvement of both other players playing together as a group
of friends) and passers-by on the streets. This is set by requiring players to for
e.g. speak to random people to find out about specific information, or activities
where players need to form a team to complete a performance.</p>
        <p>Collaboration: The Multiplayer type of challenge is one measure
implemented in the SotS to invite collaboration across players. They have to form a
team in order to have access to this type of challenges: without a team, the
challenges that are listed within a given radius from the player’s location do
not include Multiplayer ones. Only when a team is formed, the player receives
a list of Multiplayer challenges surrounding him/her and his/her fellow team
members. On top of this design choice, collaboration is also more subtly
proposed in specific challenge ideas where some sort of brainstorm or
engagement with strangers is required. In the former case, ideas such as creating a
poem do invite discussion in-between a group of players for the best poem,
and, in the latter case, peer group support can help less extrovert players in
such engagement.</p>
        <p>Digital Interaction: This form of interaction is implemented with
asynchronous message exchange through QR codes attached to the Hunter challenges.
Players can leave messages behind within these QR codes, which are then
scanned and seen by other players. Another form of indirect digital interaction
is through the voting mechanism of Voting challenges: voting a picture does
provide feedback to the creations of players. Lastly, digital interaction also
occurs when players have to scan each other’s QR codes, both to increase the
number of people met, and to form a team of players.</p>
        <p>Ownership: This game dynamic is implemented through the online
participatory system that allows players to introduce new challenges into the game. By
doing so, players own part of what is shown in the SotS to players, as they
share potentially unique knowledge about the neighbourhood with the
community of players.</p>
        <p>Winning Condition: Competition as a dynamic is set in the game firstly with
the Timed Task challenges, as it allows for competition for the fastest
performances. Secondly, the game offers points and badges throughout the
gameplay, which places not only players but also teams of players in leader boards
seen by every player.</p>
        <p>Collection: This dynamic is indirectly implemented with the possibility of
searching for real objects and scanning their QR code (of Hunter challenges).
These QR codes are not meant for players to trade or own the objects, but to
allow players to advance their condition in the game by completing challenges,
getting rewards with it, and climbing the leader boards.</p>
        <p>Exertion: The SotS invites players to perform activities involving physical
effort in Multiplayer challenges, that often require exertion (e.g. do parkour).
More indirectly, challenges involving physical performances (e.g. being the
first at spotting a white license plate) or talking to at least a given number of
people within a time frame (e.g. convince 10 people to travel by metro within
2 minutes) also invite players to rush around the environment.</p>
        <p>Virtual Representation: SotS implements an avatar, that is randomly
attributed to players when they first enter the game. This avatar can be changed
by the players by going into the settings menu, and introducing a URL of an
image that can be found via an internet search engine (and copy-pasted into
the game). This enables players to represent themselves in the way they wish
to.</p>
        <p>Mission: The entire SotS is built around small “missions” or challenges that
fall within the common theme “Secrets of the South”, meant for players to find
the secrets [of Rotterdam] and engage with the neighbourhood and its citizens,
mandating the development of 21st century social skills.</p>
        <p>Community Contribution: The challenge designs provided by SotS, 1) based
on what users want, and 2) tailored for social interaction in public space,
include passers-by, but also improvement of the neighbourhood. This
improvement is done by for e.g. cleaning trash on the street or having players doing
volunteering such as carrying bags for people, which are implemented within
Voting challenges.</p>
        <p>Lottery: Serendipity is indirectly implemented in the game by allowing
players to add new challenges to SotS. This means that players never know when
new challenges are available in the game until they open the mobile
application to play (or go to the online SotS portal and zoom into their
neighbourhood).
8.4</p>
      </sec>
      <sec id="sec-8-3">
        <title>Separation of Content from Functionality, and Implementation of the architecture with its key components</title>
        <p>
          One of the design choices of SotS was the implementation of an online content
management system (CMS), which, from the lessons learned from [
          <xref ref-type="bibr" rid="ref64">64</xref>
          ] (the essential
modules of participation and administration), resulted in the CMS being named SotS
participatory system (Fig. 7). A justification for the creation of a CMS is the need to
separate the content of the game from the development of the hard-coded functionality
leading to the game. Different challenge designs had to be prepared and offered per
case study (e.g., those reported in [
          <xref ref-type="bibr" rid="ref31">31</xref>
          ] and [
          <xref ref-type="bibr" rid="ref30">30</xref>
          ]), and having such design choice of
separating the challenge designs from the hard-coded functionality enabled a more
dynamic adaptation of the game to the different case studies. This, for e.g., allows for the
quick introduction of the several game ideas participants had, to test them in their own
game play. This led to the implementation of an online information system in three
stages: during the first stage of development, challenges were put into the system and
synchronised with the mobile game application; during second stage, players were able
to introduce these challenges themselves; during the third stage, an administrator
double checked the content proposed by players on appropriateness (e.g. foul language, or
unsafe locations), and was given the option to introduce challenges him/herself. The
first stage is a design choice that enabled the referred loose-coupling between the
content of the game (the challenges) and the game world in itself. The second stage is in
line with the essential architectural module of participation from [
          <xref ref-type="bibr" rid="ref64">64</xref>
          ], providing players
a contributing role in the game that contributes to a recurrent game play over time. The
third stage is in line with the essential architectural module of administration from [
          <xref ref-type="bibr" rid="ref64">64</xref>
          ],
to enable centralized coordination and upkeeping of the entire game, the content of the
game, the players, and their statistics, all the while proposing challenges as well.
        </p>
        <p>
          The implementation of the architecture and the key components that an LBG for
social interaction should have are also available in [
          <xref ref-type="bibr" rid="ref64">64</xref>
          ].
        </p>
      </sec>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          [1]
          <string-name>
            <given-names>N. M.</given-names>
            <surname>Avouris</surname>
          </string-name>
          and
          <string-name>
            <given-names>N.</given-names>
            <surname>Yiannoutsou</surname>
          </string-name>
          ,
          <article-title>"A review of mobile location-based games for learning across physical and virtual spaces,"</article-title>
          <source>J. UCS</source>
          , vol.
          <volume>18</volume>
          , no.
          <issue>15</issue>
          , pp.
          <fpage>2120</fpage>
          -
          <lpage>2142</lpage>
          ,
          <year>2012</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          [2]
          <string-name>
            <given-names>T. M.</given-names>
            <surname>Căşvean</surname>
          </string-name>
          ,
          <article-title>"Serious Games: Oxymoron or opportunity to increase the interest towards education and learning?,"</article-title>
          <source>in Conference proceedings of eLearning and Software for Education (eLSE)</source>
          ,
          <year>2015</year>
          , no.
          <issue>02</issue>
          , pp.
          <fpage>41</fpage>
          -
          <lpage>49</lpage>
          : “
          <string-name>
            <surname>Carol</surname>
            <given-names>I</given-names>
          </string-name>
          ” National Defence University Publishing House.
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          [3]
          <string-name>
            <given-names>J. D.</given-names>
            <surname>Mullen</surname>
          </string-name>
          ,
          <article-title>"Location-based games and augmented reality systems,"</article-title>
          <source>ed: Google Patents</source>
          ,
          <year>2013</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          [4]
          <string-name>
            <given-names>P.</given-names>
            <surname>Das</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>o. Zhu</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L.</given-names>
            <surname>McLaughlin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Z.</given-names>
            <surname>Bilgrami</surname>
          </string-name>
          , and
          <string-name>
            <given-names>R. L.</given-names>
            <surname>Milanaik</surname>
          </string-name>
          ,
          <article-title>"Augmented reality video games: new possibilities and implications for children and adolescents,"</article-title>
          <source>Multimodal Technologies and Interaction</source>
          , vol.
          <volume>1</volume>
          , no.
          <issue>2</issue>
          , p.
          <fpage>8</fpage>
          ,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          [5]
          <string-name>
            <given-names>M.</given-names>
            <surname>Flintham</surname>
          </string-name>
          et al.,
          <article-title>"Day of the figurines: A slow narrative-driven game for mobile phones using text messaging," in Virtual Storytelling. Using Virtual Reality Technologies for Storytelling: 4th International Conference</article-title>
          , ICVS 2007,
          <article-title>Saint-</article-title>
          <string-name>
            <surname>Malo</surname>
          </string-name>
          , France,
          <fpage>167</fpage>
          -
          <lpage>175</lpage>
          ,
          <year>2007</year>
          : Springer.
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          [6]
          <string-name>
            <given-names>O.</given-names>
            <surname>Sotamaa</surname>
          </string-name>
          ,
          <article-title>"All The World's A Botfighter Stage: Notes on Location-based Multi-User Gaming,"</article-title>
          <source>in Proceedings of Computer Games</source>
          and Digital Cultures Conference, ed.
          <source>Frans Mayra</source>
          , Tampere, Finland,
          <fpage>35</fpage>
          -
          <lpage>44</lpage>
          ,
          <year>2002</year>
          : Tampere University Press.
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          [7]
          <string-name>
            <given-names>A.</given-names>
            <surname>Pyae</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Luimula</surname>
          </string-name>
          , and
          <string-name>
            <given-names>J.</given-names>
            <surname>Smed</surname>
          </string-name>
          ,
          <article-title>"Investigating Players' Engagement, Immersion, and Experiences in Playing Pokémon Go,"</article-title>
          <source>in C&amp;C '17 Proceedings of the 2017 ACM SIGCHI Conference on Creativity and Cognition</source>
          , New York, NY, USA,
          <fpage>247</fpage>
          -
          <lpage>251</lpage>
          ,
          <year>2017</year>
          , pp.
          <fpage>247</fpage>
          -
          <lpage>251</lpage>
          : ACM.
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          [8]
          <string-name>
            <given-names>A. M.</given-names>
            <surname>Clark</surname>
          </string-name>
          and
          <string-name>
            <given-names>M. T.</given-names>
            <surname>Clark</surname>
          </string-name>
          ,
          <article-title>"Pokémon Go and research: Qualitative, mixed methods research, and the supercomplexity of interventions,"</article-title>
          <source>International Journal of Qualitative Methods</source>
          , vol.
          <volume>15</volume>
          , no.
          <issue>1</issue>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          [9]
          <string-name>
            <given-names>H.</given-names>
            <surname>Hodson</surname>
          </string-name>
          ,
          <article-title>"Google's Ingress game is a gold mine for augmented reality,"</article-title>
          <source>NewScientist</source>
          , vol.
          <volume>216</volume>
          , no.
          <issue>2893</issue>
          ,
          <year>2012</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          [10]
          <string-name>
            <given-names>J.</given-names>
            <surname>Peitz</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.</given-names>
            <surname>Saarenpää</surname>
          </string-name>
          , and
          <string-name>
            <given-names>S.</given-names>
            <surname>Björk</surname>
          </string-name>
          ,
          <article-title>"Insectopia: exploring pervasive games through technology already pervasively available,"</article-title>
          <source>in ACE '07 Proceedings of the international conference on Advances in computer entertainment</source>
          technology New York, NY, USA,
          <fpage>107</fpage>
          -
          <lpage>114</lpage>
          ,
          <year>2007</year>
          , pp.
          <fpage>107</fpage>
          -
          <lpage>114</lpage>
          : ACM.
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          [11]
          <string-name>
            <given-names>H.</given-names>
            <surname>Korhonen</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.</given-names>
            <surname>Saarenpää</surname>
          </string-name>
          , and
          <string-name>
            <given-names>J.</given-names>
            <surname>Paavilainen</surname>
          </string-name>
          ,
          <article-title>"Pervasive Mobile Games-A New Mindset for Players and Developers," in Markopoulos P</article-title>
          .,
          <string-name>
            <surname>de Ruyter</surname>
            <given-names>B.</given-names>
          </string-name>
          , IJsselsteijn W.,
          <string-name>
            <surname>Rowland</surname>
            <given-names>D</given-names>
          </string-name>
          . (eds) Fun and Games.
          <source>Fun and Games 2008. Lecture Notes in Computer Science</source>
          , vol
          <volume>5294</volume>
          , Berlin, Heidelberg,
          <year>2008</year>
          , pp.
          <fpage>21</fpage>
          -
          <lpage>32</lpage>
          : Springer.
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          [12]
          <string-name>
            <given-names>K.</given-names>
            <surname>Papangelis</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Metzger</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.</given-names>
            <surname>Sheng</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.-N.</given-names>
            <surname>Liang</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Chamberlain</surname>
          </string-name>
          , and
          <string-name>
            <given-names>T.</given-names>
            <surname>Cao</surname>
          </string-name>
          ,
          <article-title>"Conquering the city: Understanding perceptions of mobility and human territoriality in location-based mobile games,"</article-title>
          <source>Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies</source>
          , vol.
          <volume>1</volume>
          , no.
          <issue>3</issue>
          , p.
          <fpage>90</fpage>
          ,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          [13]
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          , G. Slingerland,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Designing for Meaningful Social Interaction in Digital Serious Games,"</article-title>
          <source>Entertainment Computing</source>
          ,
          <year>2020</year>
          . https://doi.org/10.1016/j.entcom.
          <year>2020</year>
          .100385
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          [14]
          <string-name>
            <given-names>D. f. C. a. L.</given-names>
            <surname>Government</surname>
          </string-name>
          ,
          <article-title>"Guidance on meaningful interaction: How encouraging positive relationships between people can help build community cohesion</article-title>
          .,
          <string-name>
            <surname>"</surname>
            <given-names>NCF</given-names>
          </string-name>
          , National Community Forum,
          <source>Communities and Local Government978-1-4098-0961-6</source>
          ,
          <year>2009</year>
          , Available: https://rqvvs.qc.ca/documents/file/Dossiers/guidanceonmeaningfullinteraction.pdf.
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          [15]
          <string-name>
            <given-names>B.</given-names>
            <surname>Stokes</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Dols</surname>
          </string-name>
          ,
          <article-title>and</article-title>
          <string-name>
            <given-names>A.</given-names>
            <surname>Hill</surname>
          </string-name>
          ,
          <article-title>"Cities remix a playful platform: prominent experiments to embed Pokémon GO, from open streets to neighborhood libraries</article-title>
          . American University, Washington, DC," ed,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          [16]
          <string-name>
            <given-names>G.</given-names>
            <surname>Gay</surname>
          </string-name>
          and
          <string-name>
            <given-names>T. C.</given-names>
            <surname>Howard</surname>
          </string-name>
          ,
          <article-title>"Multicultural teacher education for the 21st century," The teacher educator</article-title>
          , vol.
          <volume>36</volume>
          , no.
          <issue>1</issue>
          , pp.
          <fpage>1</fpage>
          -
          <lpage>16</lpage>
          ,
          <year>2000</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          [17]
          <string-name>
            <given-names>T. E.</given-names>
            <surname>Midgette</surname>
          </string-name>
          and
          <string-name>
            <given-names>S. S.</given-names>
            <surname>Meggert</surname>
          </string-name>
          ,
          <article-title>"Multicultural counseling instruction: A challenge for faculties in the 21st century,"</article-title>
          <source>Journal of Counseling &amp; Development</source>
          , vol.
          <volume>70</volume>
          , no.
          <issue>1</issue>
          , pp.
          <fpage>136</fpage>
          -
          <lpage>141</lpage>
          ,
          <year>1991</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          [18]
          <string-name>
            <given-names>C. F.</given-names>
            <surname>Diaz</surname>
          </string-name>
          ,
          <article-title>"The next millenium: a multicultural imperative for education," Multicultural education for the 21st century</article-title>
          . Washington, SRS/NEA, pp.
          <fpage>12</fpage>
          -
          <lpage>22</lpage>
          ,
          <year>1992</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref19">
        <mixed-citation>
          [19]
          <string-name>
            <given-names>C.</given-names>
            <surname>Diaz</surname>
          </string-name>
          ,
          <article-title>Multicultural Education for the 21st Century</article-title>
          . NEA School Restructuring Series. ERIC,
          <year>1992</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref20">
        <mixed-citation>
          [20]
          <string-name>
            <given-names>D. W.</given-names>
            <surname>Sue</surname>
          </string-name>
          ,
          <string-name>
            <given-names>P.</given-names>
            <surname>Arredondo</surname>
          </string-name>
          , and
          <string-name>
            <given-names>R. J.</given-names>
            <surname>McDavis</surname>
          </string-name>
          ,
          <article-title>"Multicultural counseling competencies and standards: A call to the profession,"</article-title>
          <source>Journal of Counseling &amp; Development</source>
          , vol.
          <volume>70</volume>
          , no.
          <issue>4</issue>
          , pp.
          <fpage>477</fpage>
          -
          <lpage>486</lpage>
          ,
          <year>1992</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref21">
        <mixed-citation>
          [21]
          <string-name>
            <given-names>M.</given-names>
            <surname>Qian</surname>
          </string-name>
          and
          <string-name>
            <given-names>K. R.</given-names>
            <surname>Clark</surname>
          </string-name>
          ,
          <article-title>"Game-based Learning and 21st century skills: A review of recent research," Computers in Human Behavior</article-title>
          , vol.
          <volume>63</volume>
          , pp.
          <fpage>50</fpage>
          -
          <lpage>58</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref22">
        <mixed-citation>
          [22]
          <string-name>
            <given-names>L.</given-names>
            <surname>Oppermann</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Schaal</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Eisenhardt</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Brosda</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.</given-names>
            <surname>Müller</surname>
          </string-name>
          , and
          <string-name>
            <given-names>S.</given-names>
            <surname>Bartsch</surname>
          </string-name>
          ,
          <article-title>"Move, Interact, Learn, Eat-A Toolbox for Educational Location-Based Games,"</article-title>
          <source>in International Conference on Advances in Computer Entertainment</source>
          ,
          <year>2017</year>
          , pp.
          <fpage>774</fpage>
          -
          <lpage>794</lpage>
          : Springer.
        </mixed-citation>
      </ref>
      <ref id="ref23">
        <mixed-citation>
          [23]
          <string-name>
            <given-names>O.</given-names>
            <surname>Rashid</surname>
          </string-name>
          ,
          <string-name>
            <surname>I. Mullins</surname>
          </string-name>
          ,
          <string-name>
            <given-names>P.</given-names>
            <surname>Coulton</surname>
          </string-name>
          , and
          <string-name>
            <given-names>R.</given-names>
            <surname>Edwards</surname>
          </string-name>
          ,
          <article-title>"Extending cyberspace: location based games using cellular phones," Computers in Entertainment (CIE)</article-title>
          , vol.
          <volume>4</volume>
          , no.
          <issue>1</issue>
          , pp.
          <fpage>4</fpage>
          -
          <lpage>es</lpage>
          ,
          <year>2006</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref24">
        <mixed-citation>
          [24]
          <string-name>
            <given-names>J.</given-names>
            <surname>Paavilainen</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.</given-names>
            <surname>Korhonen</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Alha</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Stenros</surname>
          </string-name>
          , E. Koskinen, and
          <string-name>
            <given-names>F.</given-names>
            <surname>Mayra</surname>
          </string-name>
          ,
          <article-title>"The Pokémon GO experience: A location-based augmented reality mobile game goes mainstream,"</article-title>
          <source>in Proceedings of the 2017 CHI conference on human factors in computing systems</source>
          ,
          <year>2017</year>
          , pp.
          <fpage>2493</fpage>
          -
          <lpage>2498</lpage>
          : ACM.
        </mixed-citation>
      </ref>
      <ref id="ref25">
        <mixed-citation>
          [25]
          <string-name>
            <given-names>B. E.</given-names>
            <surname>Schlatter</surname>
          </string-name>
          and
          <string-name>
            <given-names>A. R.</given-names>
            <surname>Hurd</surname>
          </string-name>
          ,
          <article-title>"Geocaching: 21st-century hide-and-</article-title>
          <string-name>
            <surname>seek</surname>
          </string-name>
          ,
          <source>" Journal of Physical Education, Recreation &amp; Dance</source>
          , vol.
          <volume>76</volume>
          , no.
          <issue>7</issue>
          , pp.
          <fpage>28</fpage>
          -
          <lpage>32</lpage>
          ,
          <year>2005</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref26">
        <mixed-citation>
          [26]
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Requirements for Location-based Games for Social Interaction," 2020 (Submitted to IEEE Transactions on Games, currently in review).</article-title>
        </mixed-citation>
      </ref>
      <ref id="ref27">
        <mixed-citation>
          [27]
          <string-name>
            <given-names>J.</given-names>
            <surname>Holopainen</surname>
          </string-name>
          ,
          <article-title>"</article-title>
          <source>Integrated Project on Pervasive Gaming: Final Report on Massively Multiplayer Mobile," IPerG2008.</source>
        </mixed-citation>
      </ref>
      <ref id="ref28">
        <mixed-citation>
          [28]
          <string-name>
            <given-names>M.</given-names>
            <surname>Bell</surname>
          </string-name>
          et al.,
          <article-title>"Interweaving mobile games with everyday life,"</article-title>
          <source>in Proceedings of the SIGCHI conference on Human Factors in computing systems</source>
          ,
          <year>2006</year>
          , pp.
          <fpage>417</fpage>
          -
          <lpage>426</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref29">
        <mixed-citation>
          [29]
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          ,
          <string-name>
            <given-names>H.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Tiemersma</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Requirements and Game Ideas for Social Interaction in Mobile Outdoor Games," CHI PLAY '17 Extended Abstracts, Publication of the Annual Symposium on Computer-Human Interaction in Play</article-title>
          , pp.
          <fpage>331</fpage>
          -
          <lpage>337</lpage>
          ,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref30">
        <mixed-citation>
          [30]
          <string-name>
            <given-names>G.</given-names>
            <surname>Slingerland</surname>
          </string-name>
          ,
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Location-based Challenges for Playful Neighbourhood Exploration," 2020 (Submitted to the Journal Behaviour</article-title>
          &amp; Information Technology, currently in review).
        </mixed-citation>
      </ref>
      <ref id="ref31">
        <mixed-citation>
          [31]
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Fostering Social Interaction in Playful Cities," in Interactivity, Game Creation</article-title>
          , Design, Learning, and Innovation, vol.
          <volume>265</volume>
          ,
          <article-title>Part of the Lecture Notes of the Institute for Computer Sciences, Social Informatics</article-title>
          and Telecommunications Engineering book series: Springer,
          <year>2018</year>
          , pp.
          <fpage>286</fpage>
          -
          <lpage>295</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref32">
        <mixed-citation>
          [32]
          <string-name>
            <given-names>J.</given-names>
            <surname>Gião</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Sarraipa</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Francisco-Xavier</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Ferreira</surname>
          </string-name>
          ,
          <string-name>
            <given-names>R.</given-names>
            <surname>Jardim-Goncalves</surname>
          </string-name>
          , and
          <string-name>
            <given-names>M.</given-names>
            <surname>Zdravković</surname>
          </string-name>
          ,
          <article-title>"Profiling Based on Music and Physiological State," in I-ESA'16: Interoperability for Enterprise Systems</article-title>
          and Applications,
          <year>2016</year>
          , pp.
          <fpage>1</fpage>
          -
          <lpage>12</lpage>
          :
          <string-name>
            <surname>I-ESA</surname>
          </string-name>
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref33">
        <mixed-citation>
          [33]
          <string-name>
            <surname>G.</surname>
          </string-name>
          <article-title>a. Grant, "On competence: A critical analysis of competence-based reforms in higher education</article-title>
          ," ed: San Francisco: Jossey-Bass,
          <year>1979</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref34">
        <mixed-citation>
          [34]
          <string-name>
            <given-names>M.</given-names>
            <surname>Romero</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Usart</surname>
          </string-name>
          , and
          <string-name>
            <given-names>M.</given-names>
            <surname>Ott</surname>
          </string-name>
          ,
          <article-title>"Can serious games contribute to developing and sustaining 21st century skills?," Games and culture</article-title>
          , vol.
          <volume>10</volume>
          , no.
          <issue>2</issue>
          , pp.
          <fpage>148</fpage>
          -
          <lpage>177</lpage>
          ,
          <year>2015</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref35">
        <mixed-citation>
          [35]
          <string-name>
            <given-names>J.</given-names>
            <surname>Voogt</surname>
          </string-name>
          and
          <string-name>
            <given-names>N. P.</given-names>
            <surname>Roblin</surname>
          </string-name>
          ,
          <article-title>"A comparative analysis of international frameworks for 21st century competences: Implications for national curriculum policies," Journal of curriculum studies</article-title>
          , vol.
          <volume>44</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>299</fpage>
          -
          <lpage>321</lpage>
          ,
          <year>2012</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref36">
        <mixed-citation>
          [36]
          <string-name>
            <given-names>M.</given-names>
            <surname>Pivec</surname>
          </string-name>
          ,
          <article-title>"Play and learn: potentials of game‐based learning,"</article-title>
          <source>British Journal of Educational Technology</source>
          , vol.
          <volume>38</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>387</fpage>
          -
          <lpage>393</lpage>
          ,
          <year>2007</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref37">
        <mixed-citation>
          [37]
          <string-name>
            <surname>M. D.</surname>
            Kickmeier-Rust and
            <given-names>D.</given-names>
          </string-name>
          <string-name>
            <surname>Albert</surname>
          </string-name>
          ,
          <article-title>"A domain model for smart 21st century skills training in game-based virtual worlds,"</article-title>
          <source>in 2012 IEEE 12th International Conference on Advanced Learning Technologies</source>
          ,
          <year>2012</year>
          , pp.
          <fpage>680</fpage>
          -
          <lpage>681</lpage>
          : IEEE.
        </mixed-citation>
      </ref>
      <ref id="ref38">
        <mixed-citation>
          [38]
          <string-name>
            <given-names>J.</given-names>
            <surname>Kirriemuir</surname>
          </string-name>
          and
          <string-name>
            <given-names>A.</given-names>
            <surname>McFarlane</surname>
          </string-name>
          ,
          <article-title>"Literature review in games and learning</article-title>
          ,"
          <year>2004</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref39">
        <mixed-citation>
          [39]
          <string-name>
            <given-names>E. F.</given-names>
            <surname>Anderson</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L.</given-names>
            <surname>McLoughlin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Liarokapis</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Peters</surname>
          </string-name>
          ,
          <string-name>
            <given-names>P.</given-names>
            <surname>Petridis</surname>
          </string-name>
          , and S. De Freitas,
          <article-title>"Developing serious games for cultural heritage: a state-of-the-art review," Virtual reality</article-title>
          , vol.
          <volume>14</volume>
          , no.
          <issue>4</issue>
          , pp.
          <fpage>255</fpage>
          -
          <lpage>275</lpage>
          ,
          <year>2010</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref40">
        <mixed-citation>
          [40]
          <string-name>
            <given-names>M.</given-names>
            <surname>Mortara</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C. E.</given-names>
            <surname>Catalano</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Bellotti</surname>
          </string-name>
          , G. Fiucci,
          <string-name>
            <given-names>M.</given-names>
            <surname>Houry-Panchetti</surname>
          </string-name>
          , and
          <string-name>
            <given-names>P.</given-names>
            <surname>Petridis</surname>
          </string-name>
          ,
          <article-title>"Learning cultural heritage by serious games,"</article-title>
          <source>Journal of Cultural Heritage</source>
          , vol.
          <volume>15</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>318</fpage>
          -
          <lpage>325</lpage>
          ,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref41">
        <mixed-citation>
          [41]
          <string-name>
            <given-names>W. L.</given-names>
            <surname>Johnson</surname>
          </string-name>
          ,
          <article-title>"Serious use of a serious game for language learning,"</article-title>
          <source>Frontiers in Artificial Intelligence and Applications</source>
          , vol.
          <volume>158</volume>
          , p.
          <fpage>67</fpage>
          ,
          <year>2007</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref42">
        <mixed-citation>
          [42]
          <string-name>
            <given-names>F.</given-names>
            <surname>Vaassen</surname>
          </string-name>
          and
          <string-name>
            <given-names>W.</given-names>
            <surname>Daelemans</surname>
          </string-name>
          ,
          <article-title>"Automatic emotion classification for interpersonal communication,"</article-title>
          <source>in Proceedings of the 2nd Workshop on Computational Approaches to Subjectivity and Sentiment Analysis (WASSA 2.011)</source>
          ,
          <year>2011</year>
          , pp.
          <fpage>104</fpage>
          -
          <lpage>110</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref43">
        <mixed-citation>
          [43]
          <string-name>
            <given-names>P.</given-names>
            <surname>Häkkinen</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Bluemink</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Juntunen</surname>
          </string-name>
          ,
          <string-name>
            <surname>and I. Laakkonen</surname>
          </string-name>
          ,
          <article-title>"Multiplayer 3D game in supporting team-building activities in a work organization,"</article-title>
          <source>in 2012 IEEE 12th International Conference on Advanced Learning Technologies</source>
          ,
          <year>2012</year>
          , pp.
          <fpage>430</fpage>
          -
          <lpage>432</lpage>
          : IEEE.
        </mixed-citation>
      </ref>
      <ref id="ref44">
        <mixed-citation>
          [44]
          <string-name>
            <given-names>J.</given-names>
            <surname>Ducasse</surname>
          </string-name>
          ,
          <article-title>"Augmented Reality for Outdoor Environmental Education,"</article-title>
          in Augmented Reality in Education: Springer,
          <year>2020</year>
          , pp.
          <fpage>329</fpage>
          -
          <lpage>352</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref45">
        <mixed-citation>
          [45]
          <string-name>
            <given-names>Y.</given-names>
            <surname>Georgiou</surname>
          </string-name>
          and
          <string-name>
            <given-names>E. A.</given-names>
            <surname>Kyza</surname>
          </string-name>
          ,
          <article-title>"Relations between student motivation, immersion and learning outcomes in location-based augmented reality settings," Computers in Human Behavior</article-title>
          , vol.
          <volume>89</volume>
          , pp.
          <fpage>173</fpage>
          -
          <lpage>181</lpage>
          ,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref46">
        <mixed-citation>
          [46]
          <string-name>
            <given-names>O.</given-names>
            <surname>Smørdal</surname>
          </string-name>
          , G. Liestøl, and
          <string-name>
            <given-names>O.</given-names>
            <surname>Erstad</surname>
          </string-name>
          ,
          <article-title>"Exploring situated knowledge building using mobile augmented reality,"</article-title>
          <source>Qwerty-Open and Interdisciplinary Journal of Technology, Culture and Education</source>
          , vol.
          <volume>11</volume>
          , no.
          <issue>1</issue>
          , pp.
          <fpage>26</fpage>
          -
          <lpage>43</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref47">
        <mixed-citation>
          [47]
          <string-name>
            <given-names>A.</given-names>
            <surname>Kamarainen</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Reilly</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Metcalf</surname>
          </string-name>
          ,
          <string-name>
            <given-names>T.</given-names>
            <surname>Grotzer</surname>
          </string-name>
          , and
          <string-name>
            <given-names>C.</given-names>
            <surname>Dede</surname>
          </string-name>
          ,
          <article-title>"Using mobile locationbased augmented reality to support outdoor learning in undergraduate ecology and environmental science courses,"</article-title>
          <source>Bulletin of the Ecological Society of America</source>
          , vol.
          <volume>99</volume>
          , no.
          <issue>2</issue>
          , pp.
          <fpage>259</fpage>
          -
          <lpage>276</lpage>
          ,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref48">
        <mixed-citation>
          [48]
          <string-name>
            <given-names>G.</given-names>
            <surname>Koutromanos</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Tzortzoglou</surname>
          </string-name>
          ,
          <article-title>and</article-title>
          <string-name>
            <given-names>A.</given-names>
            <surname>Sofos</surname>
          </string-name>
          ,
          <article-title>"Evaluation of an Augmented Reality Game for Environmental Education:“Save Elli, Save the Environment”," in Research on eLearning and</article-title>
          ICT in Education: Springer,
          <year>2018</year>
          , pp.
          <fpage>231</fpage>
          -
          <lpage>241</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref49">
        <mixed-citation>
          [49]
          <string-name>
            <given-names>H. J.</given-names>
            <surname>Hwang</surname>
          </string-name>
          et al.,
          <article-title>"RNA sequencing, de novo assembly, and functional annotation of an endangered N ymphalid butterfly, F abriciana nerippe</article-title>
          F elder,
          <year>1862</year>
          ,
          <article-title>"</article-title>
          <source>Entomological Research</source>
          , vol.
          <volume>46</volume>
          , no.
          <issue>2</issue>
          , pp.
          <fpage>148</fpage>
          -
          <lpage>161</lpage>
          ,
          <year>2016</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref50">
        <mixed-citation>
          [50]
          <string-name>
            <given-names>N.</given-names>
            <surname>Bursztyn</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Walker</surname>
          </string-name>
          ,
          <string-name>
            <given-names>B.</given-names>
            <surname>Shelton</surname>
          </string-name>
          , and
          <string-name>
            <given-names>J.</given-names>
            <surname>Pederson</surname>
          </string-name>
          ,
          <article-title>"Assessment of student learning using augmented reality Grand Canyon field trips for mobile smart devices,"</article-title>
          <source>Geosphere</source>
          , vol.
          <volume>13</volume>
          , no.
          <issue>2</issue>
          , pp.
          <fpage>260</fpage>
          -
          <lpage>268</lpage>
          ,
          <year>2017</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref51">
        <mixed-citation>
          [51]
          <string-name>
            <given-names>R.</given-names>
            <surname>Dörner</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Göbel</surname>
          </string-name>
          , and
          <string-name>
            <given-names>M.</given-names>
            <surname>Kickmeier-Rust</surname>
          </string-name>
          ,
          <article-title>"Introduction to the GI-Dagstuhl Book on Entertainment Computing and Serious Games," in Entertainment Computing</article-title>
          and Serious Games: Springer,
          <year>2016</year>
          , pp.
          <fpage>1</fpage>
          -
          <lpage>16</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref52">
        <mixed-citation>
          [52]
          <string-name>
            <given-names>E. A.</given-names>
            <surname>Boyle</surname>
          </string-name>
          ,
          <string-name>
            <given-names>T. M.</given-names>
            <surname>Connolly</surname>
          </string-name>
          ,
          <string-name>
            <given-names>T.</given-names>
            <surname>Hainey</surname>
          </string-name>
          , and
          <string-name>
            <given-names>J. M.</given-names>
            <surname>Boyle</surname>
          </string-name>
          ,
          <article-title>"Engagement in digital entertainment games: A systematic review," Computers in Human Behavior</article-title>
          , vol.
          <volume>28</volume>
          , pp.
          <fpage>771</fpage>
          -
          <lpage>780</lpage>
          , May
          <year>2012</year>
          2012.
        </mixed-citation>
      </ref>
      <ref id="ref53">
        <mixed-citation>
          [53]
          <string-name>
            <given-names>C.</given-names>
            <surname>Brosda</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Bartsch</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L.</given-names>
            <surname>Oppermann</surname>
          </string-name>
          , and
          <string-name>
            <given-names>S.</given-names>
            <surname>Schaal</surname>
          </string-name>
          ,
          <article-title>"On the use of audio in the educational location based game platform MILE," in Proceedings of the 18th International Conference on Human-Computer Interaction with Mobile Devices</article-title>
          and
          <string-name>
            <given-names>Services</given-names>
            <surname>Adjunct</surname>
          </string-name>
          ,
          <year>2016</year>
          , pp.
          <fpage>1049</fpage>
          -
          <lpage>1054</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref54">
        <mixed-citation>
          [54]
          <string-name>
            <given-names>C.</given-names>
            <surname>Sik-Lanyi</surname>
          </string-name>
          et al.,
          <article-title>"How to develop serious games for social and cognitive competence of children with learning difficulties,"</article-title>
          <source>in 2017 8th IEEE International Conference on Cognitive Infocommunications (CogInfoCom)</source>
          ,
          <year>2017</year>
          , pp.
          <fpage>000321</fpage>
          -
          <lpage>000326</lpage>
          : IEEE.
        </mixed-citation>
      </ref>
      <ref id="ref55">
        <mixed-citation>
          [55]
          <string-name>
            <given-names>A.</given-names>
            <surname>Hutzler</surname>
          </string-name>
          ,
          <string-name>
            <given-names>R.</given-names>
            <surname>Wagner</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Pirker</surname>
          </string-name>
          , and
          <string-name>
            <given-names>C.</given-names>
            <surname>Gütl</surname>
          </string-name>
          ,
          <article-title>"MythHunter: gamification in an educational location-based scavenger hunt,"</article-title>
          <source>in International Conference on Immersive Learning</source>
          ,
          <year>2017</year>
          , pp.
          <fpage>155</fpage>
          -
          <lpage>169</lpage>
          : Springer.
        </mixed-citation>
      </ref>
      <ref id="ref56">
        <mixed-citation>
          [56]
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Social Cohesion Revisited: A New Definition and How to Characterize It,"</article-title>
          <source>Innovation: The European Journal of Social Science Research</source>
          , vol.
          <volume>32</volume>
          , no.
          <issue>2</issue>
          , pp.
          <fpage>231</fpage>
          -
          <lpage>253</lpage>
          ,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref57">
        <mixed-citation>
          [57]
          <string-name>
            <given-names>J.</given-names>
            <surname>Nielsen</surname>
          </string-name>
          ,
          <article-title>"Iterative user-interface design,"</article-title>
          <source>Computer</source>
          , vol.
          <volume>26</volume>
          , no.
          <issue>11</issue>
          , pp.
          <fpage>32</fpage>
          -
          <lpage>41</lpage>
          ,
          <year>1993</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref58">
        <mixed-citation>
          [58]
          <string-name>
            <given-names>J. D.</given-names>
            <surname>Gould</surname>
          </string-name>
          and
          <string-name>
            <given-names>C.</given-names>
            <surname>Lewis</surname>
          </string-name>
          ,
          <article-title>"Designing for usability: key principles and what designers think,"</article-title>
          <source>Communications of the ACM</source>
          , vol.
          <volume>28</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>300</fpage>
          -
          <lpage>311</lpage>
          ,
          <year>1985</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref59">
        <mixed-citation>
          [59]
          <string-name>
            <given-names>A.</given-names>
            <surname>Dix</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A. J.</given-names>
            <surname>Dix</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Finlay</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G. D.</given-names>
            <surname>Abowd</surname>
          </string-name>
          , and
          <string-name>
            <given-names>R.</given-names>
            <surname>Beale</surname>
          </string-name>
          ,
          <article-title>Human-computer interaction</article-title>
          .
          <source>Pearson Education</source>
          ,
          <year>2003</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref60">
        <mixed-citation>
          [60]
          <string-name>
            <given-names>R. A.</given-names>
            <surname>Ballagas</surname>
          </string-name>
          et al.,
          <article-title>"REXplorer: a mobile, pervasive spell-casting game for tourists," in CHI'07 extended abstracts on Human factors in computing systems</article-title>
          ,
          <year>2007</year>
          , pp.
          <fpage>1929</fpage>
          -
          <lpage>1934</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref61">
        <mixed-citation>
          [61]
          <string-name>
            <given-names>H.</given-names>
            <surname>Ishii</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Kobayashi</surname>
          </string-name>
          , and
          <string-name>
            <given-names>K.</given-names>
            <surname>Arita</surname>
          </string-name>
          ,
          <article-title>"Iterative design of seamless collaboration media,"</article-title>
          <source>Communications of the ACM</source>
          , vol.
          <volume>37</volume>
          , no.
          <issue>8</issue>
          , pp.
          <fpage>83</fpage>
          -
          <lpage>97</lpage>
          ,
          <year>1994</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref62">
        <mixed-citation>
          [62]
          <string-name>
            <given-names>G. S.</given-names>
            <surname>Bailey</surname>
          </string-name>
          ,
          <article-title>"Iterative methodology and designer training in human-computer interface design,"</article-title>
          <source>in Proceedings of the INTERACT'93 and CHI'93 conference on Human factors in computing systems</source>
          ,
          <year>1993</year>
          , pp.
          <fpage>198</fpage>
          -
          <lpage>205</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref63">
        <mixed-citation>
          [63]
          <string-name>
            <given-names>S.</given-names>
            <surname>Gossain</surname>
          </string-name>
          and
          <string-name>
            <given-names>B.</given-names>
            <surname>Anderson</surname>
          </string-name>
          ,
          <article-title>"An iterative-design model for reusable object-oriented software,"</article-title>
          <source>ACM SIGPLAN Notices</source>
          , vol.
          <volume>25</volume>
          , no.
          <issue>10</issue>
          , pp.
          <fpage>12</fpage>
          -
          <lpage>27</lpage>
          ,
          <year>1990</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref64">
        <mixed-citation>
          [64]
          <string-name>
            <given-names>X.</given-names>
            <surname>Fonseca</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Lukosch</surname>
          </string-name>
          , and
          <string-name>
            <given-names>F.</given-names>
            <surname>Brazier</surname>
          </string-name>
          ,
          <article-title>"Modular Software Architecture for Location-based Games Designed for Social Interaction in Public Space," 2020 (Submitted to Entertainment Computing Journal</article-title>
          , currently in review).
        </mixed-citation>
      </ref>
      <ref id="ref65">
        <mixed-citation>
          [65]
          <string-name>
            <given-names>A.</given-names>
            <surname>Poplin</surname>
          </string-name>
          ,
          <article-title>"Playful public participation in urban planning: A case study for online serious games," Computers, environment and urban systems</article-title>
          , vol.
          <volume>36</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>195</fpage>
          -
          <lpage>206</lpage>
          ,
          <year>2012</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref66">
        <mixed-citation>
          [66]
          <string-name>
            <given-names>K.</given-names>
            <surname>Ananiadou</surname>
          </string-name>
          and
          <string-name>
            <given-names>M.</given-names>
            <surname>Claro</surname>
          </string-name>
          ,
          <article-title>"21st Century Skills and Competences for New Millennium Learners in OECD Countries</article-title>
          .
          <source>OECD Education Working Papers, No. 41," OECD Publishing (NJ1)</source>
          ,
          <year>2009</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref67">
        <mixed-citation>
          [67]
          <string-name>
            <given-names>C.</given-names>
            <surname>Lemke</surname>
          </string-name>
          ,
          <article-title>"enGauge 21st Century Skills: Digital Literacies for a Digital Age,"</article-title>
          <year>2002</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref68">
        <mixed-citation>
          [68]
          <string-name>
            <given-names>P.</given-names>
            <surname>Griffin</surname>
          </string-name>
          and
          <string-name>
            <given-names>E.</given-names>
            <surname>Care</surname>
          </string-name>
          ,
          <article-title>Assessment and teaching of 21st century skills: Methods and approach</article-title>
          . Springer,
          <year>2014</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref69">
        <mixed-citation>
          [69]
          <string-name>
            <given-names>P. D.</given-names>
            <surname>Bardis</surname>
          </string-name>
          ,
          <article-title>"Social interaction and social processes,"</article-title>
          <source>Social Science</source>
          , vol.
          <volume>54</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>147</fpage>
          -
          <lpage>167</lpage>
          ,
          <year>1979</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref70">
        <mixed-citation>
          [70]
          <string-name>
            <given-names>E.</given-names>
            <surname>Goffman</surname>
          </string-name>
          ,
          <article-title>Encounters: Two studies in the sociology of interaction</article-title>
          .
          <source>Ravenio Books</source>
          ,
          <year>1961</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref71">
        <mixed-citation>
          [71]
          <string-name>
            <given-names>E.</given-names>
            <surname>Goffman</surname>
          </string-name>
          ,
          <article-title>Behavior in public places</article-title>
          .
          <source>Simon and Schuster</source>
          ,
          <year>2008</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref72">
        <mixed-citation>
          [72]
          <string-name>
            <surname>M. d. Lange</surname>
          </string-name>
          ,
          <article-title>"The Playful City: Using Play and Games to Foster Citizen Participation," in Social Technologies</article-title>
          and
          <string-name>
            <given-names>Collective</given-names>
            <surname>Intelligence</surname>
          </string-name>
          , A. Skaržauskienė, Ed.,
          <year>2015</year>
          , pp.
          <fpage>426</fpage>
          -
          <lpage>434</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref73">
        <mixed-citation>
          [73]
          <string-name>
            <given-names>U.</given-names>
            <surname>Hagen</surname>
          </string-name>
          ,
          <article-title>"Designing for player experience: How professional game developers communicate design visions,"</article-title>
          <source>Journal of Gaming &amp; Virtual Worlds</source>
          , vol.
          <volume>3</volume>
          , no.
          <issue>3</issue>
          , pp.
          <fpage>259</fpage>
          -
          <lpage>275</lpage>
          ,
          <year>2011</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref74">
        <mixed-citation>
          [74]
          <string-name>
            <given-names>J.</given-names>
            <surname>Schell</surname>
          </string-name>
          ,
          <article-title>The Art of Game Design: A Book of Lenses</article-title>
          . Morgan Kauphann Publishers: Morgan Kauphann,
          <year>2008</year>
          .
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>