Serious Games Accessibility Design Model for Low-Vision Children

. Te evolution in information technology has brought worldwide access to information. Information technology has become an approach for efective learning in the education sector. Tis development provides an opportunity for people with disabilities. However, many educational software and applications in the market, such as serious games, cannot be accessed by low-vision children due to the visual properties in game design. For instance, small text and graphic sizes, lack of colour contrast, complex visual efects, or reliance on visual cues for instructions are among the visual properties that contribute to these accessibility challenges. Tey can play serious games as long as they are designed based on their accessibility needs. Tis paper proposed a serious games design model for low-vision children. Te three main components are accessibility, game design, and pedagogy. Te serious game accessibility design model is implemented using a low-fdelity prototype that takes the form of a serious game mockup. Tis prototype allows for basic interaction and testing of the game’s features, with a focus on accessibility considerations. Te expert validation was conducted on the prototype using heuristic evaluation to assess its usability. Based on the evaluation, the experts agreed on implementing the proposed model to the prototype.


Introduction
Te evolution of IT has transformed educational opportunities, particularly benefting individuals with disabilities.In the education sector, IT has become an efective approach for learning.Tis development provides opportunities for disabled people.Previous research has shown that IT afects the life of disabled people [1].Tere are various educational software and applications for disabled people.Te disabled people in society should be treated equally in the pursuit of good quality education.Tere should not be any discrimination against them to ensure they can lead a good life regardless of their social status, race, and background.Tere are several disabilities, such as physical, mental, and cognitive.Visually impaired people are an example of physically disabled members of society who should have the opportunity of using IT and accessing information.Visually impaired people consist of two categories: blind and low vision.Low-vision people have a visual balance that can be assisted with technology.However, many educational software and applications in the market, such as serious games, cannot be used by low-vision children due to the visual design in the game.Terefore, there is a need to design a serious game that low-vision children can use.According to [1], low vision refers to vision loss that eyeglasses and treatment cannot correct.Low-vision people learn to adjust their residual vision.Visual disability does not mean that they cannot do any activities to learn new ways to perform the activities.Low-vision problems occur when the sight level of a person does not exceed 6/60 or 20/200 [2].
Low-vision children have difculties accessing graphical elements on the screen [3].Tey need to look at the tablet screen from a very close distance due to the small size of the text and graphics besides the low colour contrast.Te use of dark colours is unsuitable for them.Tey also experience difculties accessing menus and buttons in games.Audiobased instructions should also not be played simultaneously with the background audio because low-vision children can only focus on one sound at a time.Fast animation movement and the direction of animation movement can also afect their vision.Tese problems cause them to gain less satisfaction when playing games.Based on a previous requirement study [3], several accessibility requirements are visual, animation, audio, and navigation.Using their remaining vision, low-vision children can play serious games as long as they are designed based on their accessibility needs.Hence, this paper presented the requirements and proposed a conceptual model of accessibility design in serious games for low-vision children.In the following section, Section II discusses related work, while Section III describes the materials and methods.Sections IV and V discuss the results and the discussion, while Section VI presents the conclusion and plans for future work.

Related Works
Accessibility refers to how software and ICT applications can be accessed by disabled people [2,4].Accessibility is important for developers and organisations to improve the usability of ICT applications.Everyone should use hardware and software applications without thinking about their limitation.Terefore, ICT applications should be designed based on user accessibility needs.When an ICT application meets this aim, it is accessible to users with diverse cognitive abilities, hearing, movement, and sight.Te accessibility in ICT applications usually focuses on web accessibility [5].Web applications are used since the web removes barriers to communication among people around the world.Tus, if websites and other ICT applications are badly designed, they can be challenging.Te accessibility to ICT applications involves sensory, physical, and cognitive aspects.Terefore, a visually impaired user would face difculties accessing graphical-based interfaces in ICT applications.A visually impaired user with low vision can use assistive technology such as screen readers, screen magnifers, alternative keyboards, and voice recognition when using ICT applications.Assistive technologies such as screen readers and screen magnifers help users with low vision by reading text-tospeech information and improving text and images.Although many assistive technologies help low-vision users, they are abandoned because they may not support some applications, including digital games and only support text and static information [3].
Disabled users also have difculties viewing and accessing onscreen information due to the view limitation of the screen magnifer.Based on a study by [6], assistive technologies do not meet users' needs because they struggle to adjust to the changes in visual content when navigating the applications.Besides that, assistive technologies do not provide enough control for users to see the content comfortably.Te inefciency of accessing the technology makes users lose control and leaves them disoriented.Users also feel uncomfortable revealing their disability to normal users.
Furthermore, existing assistive technologies such as screen readers can burden children's cognitive abilities due to their low concentration because assistive technologies need a high concentration level.Assistive technologies are also unable to support certain ICT applications such as games due to their highly interactive systems.Terefore, a design that enhances accessibility to games is required for low-vision users.Te accessibility requirements for lowvision children need to be studied to guide the development of serious games.Tere are several models which are relevant to our study and which consist of three components such as accessibility, serious game, and pedagogy.Te next section will discuss on the previous accessibility design model which is essential for accessibility component.

Accessibility Design Model.
Several studies on accessibility, such as [7], proposed a web design model to improve the accessibility to the web for disabled people.Tis model is based on the three web components of content, navigation, and user interface.Tis model aims at presenting the design requirements of web accessibility in a developer-oriented format.Te accessible content of the web includes text, images, videos, and audio that can be accessed by all users, including disabled people.Navigation is a method of moving within the website and other pages where the navigation is accessible if disabled users can navigate the website easily.Te user interface refers to the elements users perceive and use to interact with the applications.Tus, the accessibility of content, navigation, and user interface are the primary goals of web accessibility in this framework.
A design model of educational website accessibility was proposed by [8].Based on this model, accessibility design is important to design an educational website and should be performed in each phase of the design process.An educational website design team comprises designers, developers, and learners.Learners are usually concerned with technologies and content presentation, while designers and developers focus on the functionality and safety of the educational website.Tus, the web accessibility for navigation, content, language, and links are included in this model to fll in the gaps.Besides that, a study by [9] presented a framework to select the web technology and how web design development can infuence web accessibility for disabled users.A hierarchical decision model is applied to represent the design, adaptive technology, and web technology that include attributes and requirements applied to enhance web accessibility.
Furthermore, an assistive courseware model for visually impaired users has also been proposed [10].Te model includes information accessibility, navigation, and the pleasure aspect of the courseware.In addition, the model focuses on the design of content to fulfl the needs of visually impaired learners.Another proposed courseware accessibility model is for hearing-impaired learners [11].Table 1 shows the analysis of accessibility elements from previous models and frameworks for accessibility design.
Based on the analysis, most of the accessibility models and frameworks focused on the accessibility of the web, which was static compared to ICT applications such as games that are highly interactive systems.As a result, there is a lack of accessibility design models for games.In addition, existing accessibility design models and frameworks did not 2 Advances in Human-Computer Interaction focus on game accessibility, especially for low-vision children.However, there are several previous studies on game accessibility.

Game Accessibility.
Te popularity of games today means that games should be accessible to everyone.However, disabled people encounter challenges while playing games [14,15].According to [16], accessibility problems occur when a person cannot receive feedback, determine game responses, and use conventional input devices.Although there are existing game accessibility guidelines (Independent Game Developers Association), the guidelines are only applicable to a specifc game context.Tey do not provide solutions to the accessibility issues.A disability afects the ability of a player to play games.Visually impaired users are unable to see primary stimuli.Tus, it is difcult to determine the game response.Several games are developed or modifed for visually impaired people, such as the blind, for entertainment purposes.Most games use audio for visual replacement.
Low-vision children have a residual vision that can be used to play games if the game design fulfls their accessibility requirement.Low-vision children can use computers, software, or applications designed based on their requirements.Several interface design aspects concerning lowvision children include screen design, graphic presentation, text readability, and vivid colour.Te visual elements pose a challenge to access existing games such as serious games.Based on previous studies, several accessibility elements should be applied to enhance the accessibility of serious games for low-vision children, as shown in Table 2 [15][16][17][18][19][20][21][22][23][24].
Terefore, serious games for low-vision children should be designed based on their needs.Te accessibility elements such as screen design (menu, button, and navigation), object movement, multimedia contents, language, and interactivity should be implemented in the game design based on their requirements so that the serious game is accessible to them.In the next section, we discuss on serious game component.Tere are several game design models that are relevant to this study.

Serious Game.
Abt introduced the frst concept of serious games in 1970.Tis concept was presented in war games during a project conducted by Atari in the 1980s for military training by using board and card games or pen-andpaper games.Te American army's use of serious games for tactical and strategic training allowed them to participate in simulated real-world battles [25].According to [26], a serious game is usually used for entertainment purposes but can educate players.A serious game is usually based on the game user interface and simulations, and its purpose is beyond entertainment such as training, education, healthcare, defence, communication, politics, and others [27][28][29].Te objective of a serious game is usually to teach users while providing a pleasurable experience.In learning, serious games have motivated users by providing interactive learning [30].Tere are several serious game applications for learning language, science, mathematics, and enhancing cognitive skills in solving problems [31].
Serious games are proven to produce more inspirational learning results.In addition, the element of reward in a game can establish the communication with players to continue playing.When the game elements, story narrative, and gameplay are appealing to the players, endorphin is released into their bodies and motivates them to continue playing to gain rewards.Te players will continue to play and gain information until stored in the long-term memory [26].In education, serious games are similar to educational games because both games focus on developing knowledge and skills.However, serious games are diferent from educational games in which the design of serious games is almost similar to commercial digital games for their gameplay.Te educational content is implicit in the gameplay.Studies on available educational game models and frameworks can assist in designing serious games for learning purposes.

Game Design Models and Frameworks for Learning.
Designing and developing of a game is not an easy task, and design models are important to guide developers in developing games.Tere are several models and frameworks for educational games from previous studies.A model for

Perrenoud and
Phan [9] Sun and Wen [12] Aziz et al. [13] Siti Zaharah and Nor Azan history educational game design using the digital gamebased learning (DGBL) approach was proposed by [32].Te main components consist of digital games and pedagogy.Te digital game consists of storyline, rules, immersive experience, enjoyment, feedback, multimedia technology, challenge, and reward.Te pedagogy component consists of the learning goal, learning theory, educational psychology, curriculum needs, patriotism and moral value, and the memorisation and forgetting theory.On the other hand, a conceptual model of serious games based on the learning theory was defned by [33].Tis model combines gaming requirements with the learning and pedagogy theories.Te model's components are game components, game mechanics, game genre, game achievement, capability (cognitive, psychomotor, and afective skills), instructional contents, learning outcomes, and refection.Te component of refection in this model refers to what a player thinks is the objective of the learning activities and decides the strategy during the next activity.
In addition, the game object model (GOM) was developed by [34] that combines game design with educational theory.Tis model was based on the constructivist educational theory.Te game elements trigger enjoyment and fun, while the pedagogical elements develop a learning environment.Besides, [35] proposed a model that adapted the interaction cycle in a game between users and the game.Based on this model, learners should understand the goal of each task in the game and learn the learning content.Te learner also decides the actions which should be taken to accomplish the task, and the game provides feedback to the learner.Te learner can evaluate whether he/she has given the correct information and repeat the task or move on to the next task.Table 3 summarises the analysis of the game model according to the game elements.
Based on the analysis, the common game elements used for educational games are storyline, challenge, reward, fantasy, rules, and goal.Tese elements should be considered when designing educational games.All models stress the importance of combining pedagogical principles with game design elements to create efective serious games.A combination of pedagogical and game design elements should be included in designing serious games for education [39].
In summary, this section has highlighted the evolution of serious games, emphasizing their use in various felds such as training, education, healthcare, defence, communication, and politics.Serious games aim at educating while providing an enjoyable experience and have proven to be efective tools for learning.Te section introduced several game design models and frameworks for learning, which are crucial for guiding the development of educational games.Tese models emphasize the integration of game elements and pedagogical principles, highlighting the importance of combining engaging gameplay with educational content.Te next section discusses the pedagogical aspects that underlie the design and development of serious games, enhancing our understanding of how these games can effectively facilitate learning.

Pedagogy.
Pedagogy deals with theory and practice of education as the best way for learning [40].It facilitates the acquisition of knowledge, skill, and attitudes, and the  [41].Table 4 summarises the analysis of the game model for education according to the pedagogy aspects [32][33][34][36][37][38].
Based on the analysis, several learning elements should be considered when designing educational games: learning goal, learning theory, and learning contents.Learning goals should be considered when designing educational game because the game system usually associates with the learning objectives [40].Learning goals are the specifc knowledge and skills that the game is designed to teach and should be aligned with the objectives of the game [42].Moreover, learning goals are set to promote users' knowledge [41].Besides, learning theory plays an important role in the design and development of serious games.Learning theory provides a framework for understanding how people learn and how they can be excellently taught.Te use of learning theory in serious game design allows developers to design games that are more efective in accomplishing their educational goals [33].Te learning content plays a signifcant role in accomplishing the game's goal.Te learning content provides a user with information, knowledge, and skills related to the game's subject [43].Te game's educational content is designed to meet learning goal and align with the game design such as theme, storyline, and challenges [44].It ofers opportunities for a user to learn new concepts, theories, and skills while playing the game.Well-designed learning content in serious games can develop player engagement [45].When players are interested in the game's subject, they are more likely to be engaged in the game and invested in achieving its goal.Learning content in serious games can foster skill development by providing players with opportunities to practice and improve their skills in a safe and interactive environment [45].It is designed to align with the game's objectives and ensure that users can apply what they learn when playing game.
Since most educational games focus on normal players, the accessibility elements need to be included for disabled people to access serious games for learning.Accessibility elements are important for disabled people to access serious games for learning because these elements ensure that the games are equitable and inclusive for all players, regardless of their abilities and facilitating the learning process.Disabled people are not excluded from the learning experience.Disabled people could take control of their learning and choose how they access the content.
Designing games with specifc accessibility requirements presents a challenge as it requires a deep understanding of design principles and relevant approaches.In addition, the design principles should be adapted in the game design to ensure serious games are accessible to them.Te next section will discuss the design principles of this study.

Design Approach and Principle.
Players are also important in designing a serious game because the game should be designed based on the needs of the target players.A serious game should be developed based on the requirements of players.Developers should focus on users' characteristics during the game design.Design approach and principles should be applied during the design process.Inclusive design is a design approach that aims at designing accessible and useable content for many people, including elderly and disabled people [46].Te inclusive design focuses on user-centeredness because people have diferent capabilities, skills, experiences, and opinions.Terefore, the product should be functional to satisfy the needs and desires of users.It should also be easy to operate useable products and satisfy users [47].According to the British Standard Institute in 2005, inclusive design is defned as a design of mainstream products and services accessible and useable to many people, which suggests the inclusion of people with disabilities.By understanding their needs, the inclusive design improves product experience among various users to produce a better design [48].Tus, inclusive design should be applied in the design and development process.Besides that, in the area of design education, inclusive design is a philosophy that creates beautiful and functional environments which can be used equally by everyone without concerning their age, gender, disability, and the design process that must accommodate diferent requirements of desires and expectations [49].Te inclusive design also refers to a methodology applied throughout the design and development process to produce better-designed products that are more useable and desirable.Based on the inclusive design process, there are four key stages where evaluation is conducted throughout the design cycle.Te initial need should be explored and refned to determine the real need.Figure 1 shows the stages in the inclusive design process [48].
Inclusive design has several similarities with universal design and design for all.Inclusive design, universal design, and human-centered design are overlapping design philosophies [50].America and Japan use the term "universal design," while the UK uses the term "inclusive design," and Scandinavian countries use the concept of "design for all" [47].However, we use the term "universal design" in this study.Universal design can guide the process of designing, and it is an approach to ensure that a product is used by everyone, including disabled players [10].Studies on universal design have also focused on interface technology.Several factors support the universal design of an application.Table 5 shows the elements of universal design.
Universal design is important in designing a product to be used by all users, including disabled people.Te universal design elements need to be implemented in the user interface design to produce a simple user interface that does not burden children's cognitive ability.Tis is because the development of cognitive ability varies on diferent levels.
Universal design is essential in designing a product to use both normal and disabled users.Te universal design elements need to be applied in the user interface design to produce a serious user interface design that is simple and does not burden children with cognitive impairment.Tus, it is important that the developer designs for children and children's technology principles when designing serious games.Te next design principle for accessibility is the children's technology principle.

Te Children's Technology
Principle.With increasing exposure to mobile technology, the use of ICT among children has grown.Many interactive applications help children learn, so it is essential to assess their abilities, interests, and developmental stages when designing ICT applications specifcally for them.The detailed design of the final product will be produced, leading to solutions.

6
Advances in Human-Computer Interaction Children constitute a signifcant user group for ICT applications, and their needs must be considered.Tey use these applications for both educational and entertainment purposes and possess varying levels of experience and skills.Interface design requirements for children difer signifcantly from those for adults, as children need interfaces that align with their cognitive, physical, and social development [52].Table 6 lists the important aspects to consider when designing interfaces for children [52,53].
It is important to have a design that fulfls children's needs.Te children's design elements must be applied in the user interface design to produce a concise game interface and compatible with their cognitive and physical capabilities.Indirectly, the usability of serious games can be improved.

Materials and Methods
Tere are two main activities in the design phase: serious game design and expert validation.Te serious game design includes accessibility design and game design.

Serious Game Design Activities.
Te design phase includes implementing the conceptual model in the storyboard (lowfdelity prototype), where the storyboard is used as a reference to produce a prototype (high fdelity).Te low-fdelity prototype is chosen for evaluation since low-fdelity prototypes are easy to create, modify, and facilitate rapid iteration.It helps identify fundamental faws or usability issues early in the process.Te accessibility elements are applied in the design of the game interface.Game design and the pedagogy component of the game were also designed and implemented into the lowfdelity prototypes.Game design involves game elements such as storyline, challenges, rewards, fantasy, and rules, whereas the pedagogy involves learning objectives, theory, and contents.In addition, expert validation was conducted to confrm the implementation of the accessibility design model in serious games for low-vision children into the low-fdelity prototypes.

Experts' Validation.
Expert validation was conducted on the prototype using heuristic evaluation to assess its usability.Te purpose of the examination is to validate the serious game accessibility design model.
Te evaluation involved six experts from the game area, human-computer interaction, and special education.Game design experts have extensive experience in the feld of game design.Teir insights were crucial in evaluating the game mechanics and overall gaming experience aspects of the prototype.HCI specialists bring expertise in user interface and interaction design.Tey helped ensure that the user interface elements were intuitive, responsive, and conducive to a positive user experience, especially for low-vision children.Special education experts were included because they possess valuable knowledge about the specifc needs and challenges faced by low-vision children, allowing them to assess the game's appropriateness for educational purposes.Feedback from the expert evaluation was used to refne the prototype.Te low-fdelity prototype will be used as a guide in developing serious games for low-vision children.Table 7 shows the list of experts involved in the evaluation.

Instruments.
Te instruments used for this evaluation were a low-fdelity prototype and a checklist.Te researcher constructed a heuristic evaluation checklist based on the literature review, consisting of three sections: interface design, game, and learning.A list of heuristic principles [54] and heuristic evaluation for user interface [55] were adopted for the interface section in the checklist.Heuristic evaluation for games by [56,57] and heuristic for learning [58] were adopted for the checklist.

Hardware and Software.
Te hardware used for this evaluation was a tablet, while the software used was Microsoft PowerPoint to develop the low-fdelity prototype.

Evaluation Process.
Te experts were invited to participate in the evaluation, and the researcher set a date for the evaluation.During the evaluation, the researcher explained the evaluation purposes to the experts.Te researcher demonstrated the low-fdelity prototype to the experts.Next, the checklist was given to the experts.Te experts tested the low-fdelity prototype and flled in the checklist.In this evaluation, the experts' role is a regular player.Te experts need to follow the instructions and answer every question Chunking A technique where the information is combined into specifc pieces (chunks) so that the information is easy to process and remember

Colour
Limit the use of colours to at least fve colours depending on the complexity of the design.Do not use colour as the only way to convey information Consistency Te consistency: the same section is presented similarly Control Te control level provided to a system suits the abilities and experience of the user Readability Te readability of certain information is based on word size, contrast, and space Mapping Te relationship between control over a system and its efects.Good relationships can facilitate the use of a system Ockham's razor Te interface should be simplifed, and any unrelated element needs to be reduced

Performance load
Performance load consists of cognitive load and kinematic load.Te cognitive burden can be reduced with minimal design, while kinematic load involves the burden of physical activity by reducing an action or movement Advances in Human-Computer Interaction provided in the checklist with a 2-option rating scale such as yes or no.When the answer is yes, the expert agrees that the features represent good usability while no represents the opposite.When the experts completed the evaluation, the researcher analysed the data.Te experts' answers were quantifed using usability percentage [59].Yes is weighted with 1 point.No is weighted with 0 points.Te values were added to obtain the fnal value, translated to a percentage value (usability percentage).Tus, the usability percentage enabled the comparison between the design elements.Te experts provided suggestions to improve the design.
In summary, the design phase of this research encompasses two key activities such as serious game design and expert validation.Serious game design involves creating a low-fdelity prototype of the game based on the conceptual model and implementing accessibility and game design elements, including storyline, challenges, rewards, and rules, as well as the pedagogical components such as learning objectives and educational content.Expert validation is then conducted to assess the usability and adherence to the serious game accessibility design model.Te process involves serious game design and expert validation, with a focus on including experts from diverse backgrounds and utilizing

Results
Te serious game accessibility design model was developed during the design phase.Te accessibility model of a serious game for low-vision children consists of three components: accessibility for low-vision children, game design, and pedagogy.

Proposed Serious Game Accessibility Design Model.
In the accessibility for low-vision children component, universal design and children's technology design principles were used to design serious games.Several accessibility elements include multimedia, language, object movement, and screen design (menu, button, and navigation).Te multimedia elements include audio, graphics, text, and animation.For the language element, low-vision children should easily understand the language used.Te movement of objects in the game includes speed and direction.Te game design consists of two main components: the user interface and game elements.Te game elements include game contexts and gameplay design.
Te game contexts consist of the game environment, including game fantasy, goal, and storyline.Te gameplay design consists of challenges, rewards, and rules.Te game accessibility elements are adapted to the low-vision children's requirements and implemented into the serious game design as follows:

Screen Design (Buttons, Menus, and Navigation).
Te user interface design includes screen design and navigation.Te screen design consists of layouts, menus, and buttons.Te menu size and buttons should be bigger.Te colour of the menu or button should be bright and has a high contrast between the background colours to facilitate the navigation of low-vision children.Te interface designs should be simple to reduce the cognitive burden on the children and fexible to accommodate the needs of lowvision children.To ease the navigation of low-vision children, the menu layout and buttons should be simple.Te menu and buttons should also include background audio for easy navigation.Te accessibility elements are implemented in the serious game design as follows.

Multimedia.
Multimedia is important when designing a game.Te accessibility to the game can be improved through the adaptation of multimedia elements in the game context and gameplay.Several multimedia elements are implemented into the game context and gameplay as follows.

Graphic.
Te game context, such as game environment and storyline, involves a lot of graphic elements.Terefore, the graphic design must be suitable for visually impaired people.Te game environment involves the fantasy element.Te game environment should use bright colours for graphics.Besides that, the contrast between the background colour and graphics should be high and adjusted based on players' preferences.Te graphics design in the game environment should also be minimal to focus on the game's important contents.For gameplay, the game challenge should be balanced with the children's visual ability.Tus, the size of the target object in games should be bigger.Te important graphics in-game challenges should also use bold lines.

Texts.
Te game context requires the storyline with texts visible to low-vision children.In games, the size of the text should be larger.Te colour contrast between the text and background must be high, and the type of text used is serif.Important text content needs to be highlighted so that users can access important information in the game.As for the game mechanism, the rewards in the game activities should be designed with bold-type texts.
4.1.5.Audio.Audio also plays an important role in the design of game contexts, such as storyline and goals.Te game storyline includes a voice-over so that low-vision children understand the storyline clearly.Besides, the game goals are the core concept to design a game because the gaming experience is based on the goals.Te game goals should be clear and specifc to have greater persistence and enhance performance when playing a game.Te game instructions are also included with a voice-over so that lowvision children understand the game goals clearly.In addition, a positive audio sound can tell whether a task was successful.Tus, low-vision children will be notifed whether they achieve the game goals.
Besides, the gameplay requires audio to balance the game challenge and the children's visual ability.Te target object in the game challenge should be included with the background sound to make it easier for children to locate the target objects in the game.
4.1.6.Animation.Animation is one of the important elements in game design.For the game context, the animation design for the storyline should be simple.Te main characters in the game design should use a bright colour, and the characters are introduced at the beginning of the game so that children will understand the storyline.Te gameplay requires animation that assists low-vision children in completing the challenge.Some animations help children complete math tasks successfully and hint for the next action.Te game rewards are designed with animations to notify children of their rewards.

Instruments' Language.
Language is an important element of accessibility when playing a game to enable children to play better.Terefore, the language used should Advances in Human-Computer Interaction be easy to understand.For the game context, such as storyline and goals, the Malay language was chosen to enable children to understand the game's storyline and goals.

Object's Movement.
When designing a game for lowvision children, the object's movement in the game storyline and challenges can be adjusted based on the children's preference.Te object's movement should not be too fast so that the children can play well.
4.1.9.Interactivity.Interactivity refers to how low-vision children interact with the game.Low-vision children's interaction with the game is mediated by gameplay.Te game mechanism is important to achieve game goals.Te process of achieving the goals is accompanied by game challenges.Te challenge requires low-vision children's abilities, associated with the game mechanism.Mechanisms such as tasks and rewards encourage challenges and motivate children to achieve goals.Terefore, the design of interactivity for the game challenge must be adjusted based on the children's abilities.For example, based on the children's design principle, drag and drop can be used to mediate the interaction between children and the game.
Te game rules are important to defne what children should do while playing.Low-vision children communicate with the game interface and act via related game rules.When they play the game, they will comply with the rules and control them based on the rules.Te game rules are processed in the background and not accessible to the children.Tus, the game rules should be simple so that children can follow the game rules easily.
Te pedagogical component consists of learning objectives, theories, and learning content.Te learning objectives should be parallel with the game objectives.Te learning theory used is constructivism.Lastly, the learning content should be suitable for low-vision children's ability.Figure 2 shows the conceptual model of accessibility in serious games for low-vision children.

Implementation of Accessibility Design in the Low-Fidelity
Prototype.Te accessibility conceptual model of serious games for low-vision children was implemented in the lowfdelity prototype.Te purpose of the model's implementation is to improve the usability of the game.Te serious game designed for this study is a math game.Tis game is about a rabbit named Bunny who tries to save his friends that are kidnapped by a tiger.Bunny has to complete the math tasks provided for each level to save his friends.Table 8 shows the example of how the accessibility elements are implemented in the game prototype.
Examples of the interface design are shown in Figure 3.

Heuristic Evaluation Results
. A total of 6 experts had completed the heuristic evaluation to assess the accessibility, game, and learning components.Based on the evaluation of the accessibility component, the highest value of usability percentage was object's movement (100%), followed by multimedia (89%), and interactivity (87%).Te object's movement was the most satisfying aspect, which means that the object's movement was relatively good.Te experts were satisfed with the multimedia and interactivity aspects of the game.Te lowest value of usability percentage was screen design and language (76%).However, the screen design and language were still acceptable.Table 9 shows the summary of the experts' responses for the accessibility of the game based on the heuristic principle: Heuristic evaluation was also conducted on the game component.Te highest value of usability percentage was a challenge (98%), followed by a game reward (90%).Challenge was the most satisfying aspect because the game challenge was quite good.Te experts were also satisfed with the game's reward.Te goal and fantasy elements have the same value with the usability percentage (87%), where both aspects were acceptable.Te lowest value for usability percentage was storyline (80%).Table 10 shows the summary of experts' responses on game heuristics.
For the learning aspect, the highest value of usability percentage was learning objectives (100%).Te learning objectives were the most satisfying aspect.Te value of usability percentage was the same for the learning theory and learning contents, which was 87%.Te experts were satisfed with the game's learning theory and the learning contents.Table 11 shows the summary of experts' responses on pedagogy heuristics.
Te evaluation provided signifcant responses regarding the usability of the serious game design model.Te mean value of all evaluations was 88%, indicating a good usability level.However, certain aspects of the prototype need to be improved based on the feedback from experts to improve the serious game design.Table 12 shows the summary of the usability percentage for heuristic evaluation and the experts' comments to improve the serious game designs.

Discussion
Te results from the proposed model contribute to previous research in several ways.Tis study was comprehensive, including users with disabilities such as low vision.Te accessibility component ensures that the model can be used by low-vision children, thus supporting the accessibility of serious games for them.Previous research results on web accessibility models presented accessibility elements such as content (text, graphics, and animation), navigation, and user interface (buttons and menus).However, these web accessibility elements cannot be fully applied to games due to their complex graphic elements, and there are also challenges that need to be addressed in order to design accessible games.Accessibility requires specifc adaptations such as alternative controls, visual and auditory cues, captioning, or options to control difculty levels or game speed.Moreover, game accessibility may require diferent considerations for diferent types of games.Most accessibility studies provide little guidance on how to implement accessibility components in serious games because they do not take into consideration game design, thus hindering the learning process.Table 8: Implementation of accessibility elements in the prototype.

Accessibility elements Descriptions
Screen design (buttons, menus, and navigation) Simple interface design.Examples of the screen design are shown in Figures 3 and 4 (1) Te size of the buttons and menus is big (2) A bright colour is used for the menu or button and contrast the background colours.Te colour can be adjusted (3) Te menu and buttons are included with background audio to navigate the game easily

Graphic
Te graphics are designed as shown in Figure 4 (4) Te game environment uses bright colours for graphics (5) Te size of characters and target objects in the game is big (6) Te colour is high contrast and brightness (7) Te colour can be adjusted, as shown in Figure 5 Texts Te texts used are shown in Figure 4 (8) Te size of the texts is large (9) Te type of text used is serif (10) Important text content needs to be highlighted to access important information in the game Audio (11) Audio is used for storyline, character, task description, indicator, and dialogue (12) Te target object in the game challenge should be included with a background sound to assist children in locating target objects in the game, as shown in Figure 6 Animations (13) Animations are implemented to assist low-vision children in playing the game.Figure 7 shows the example of animation used in the game (14) Te animations are hints for the next action Object speed (15) Te object's movement is slow, adjustable, and in one direction (16) Te object's speed can be adjusted based on users' preferences, as shown in Figure 4 Language (17) Children should easily understand the language (18) Te Malay language is used for the game, as shown in Figure 3 Interactivity (19) Drag and drop are used as the mechanism for interaction between children and the game Advances in Human-Computer Interaction Furthermore, most previous serious game models consist of game and pedagogy components.Te use of accessibility components has demonstrated the efectiveness of serious game models.However, most serious games focus on normal players, making accessibility components important for low-vision children to ensure that games are inclusive for all players, regardless of their abilities, and facilitate the learning process.
Terefore, to address the accessibility problems and improve game design to make games more efective for learning, we propose a model that combines accessibility and pedagogy with games.Tis model aims at establishing a conceptual structure that can be used by game designers for efcient game development or by educational practitioners when designing serious games for low-vision children.Te experts were satisfed with the multimedia presentation in the game because the multimedia elements were suitable for certain purposes.Te multimedia element used in the game conveyed information to users Match between the system and the real world Te experts agreed that appropriate icons for the screen design were used and commonly seen.Te menu was arranged logically and users interacting with the screen design without difculties Experts also found that the language used was normal using acceptable words User controlling and navigation Te experts agreed with the screen design, and the game provided well navigation.Users can move to another screen efectively.Te screen design provided a way for users to leave the game directly.Users can also access the setting button based on their preferences.For interactivity, the experts can interact with the game easily.
Tus, they can control the game well Recognition rather than recall Te experts found that users did not need to remember unimportant things to proceed.Users also did not need to remember information from the previous to solve the task Aesthetic and minimalist design Te experts agreed that the game contains relevant information to minimise screen design elements.Tey found that the screen design was simple and understandable

Challenges
Te experts agreed that the challenges provided a positive experience since the challenges and strategies are balance.Te challenge in the game did not disappoint users and changed from easy level to difcult level Rewards Te rewards were acceptable, and the experts were satisfed with the rewards Goal Te experts agreed that the game's goal was clear, and the gameplay supported the goal Fantasy Te experts were also satisfed with the game fantasy because they could control the game world.Te game fantasy attracted users to play the game Storyline Te experts found that the storyline supported the gameplay.Te storyline was easy to understand, and the experts were interested in the storyline.Te background story and the game were consistent  (ii) Provide animations in the menu section so that users will choose the menu better (iii) the graphic presentation (iv) Provide background audio for the target objects in the game.For example, there is a sound when the rabbit collects the carrot, which helps users recognise the exact location of the carrots

Conclusion
Tere are three key components of the game-based accessibility model regarding the serious game accessibility of low-vision children: accessibility components, game design components, and pedagogical components.Te conceptual model is implemented into a low-fdelity serious game prototype for low-vision children.Based on the experts' evaluation, they agreed on implementing the proposed conceptual model into the prototype.Te prototype will be refned based on the experts' comments.Terefore, the study presented a comprehensive model for serious game accessibility tailored to low-vision children, encompassing accessibility, game design, and pedagogical components.
Te successful agreement among experts on implementing this model into a low-fdelity prototype marks an important milestone in addressing the specifc needs of this underserved user group.In the broader feld of game design for low-vision children, this research can have implications.
Te design of serious games is a complicated process that involves a range of challenges.Te game's design must strike a balance between entertainment and educational elements because if the game is too focused on learning, it may become boring and fail to achieve its intended outcomes.Accessibility elements must also be integrated carefully into the game design to ensure that the game is accessible to all users, including low-vision children who need to understand the game's storyline easily.Tis fnding is relevant not only for low-vision children but for game designers, aiming to create inclusive and engaging experiences for diverse audiences.By emphasizing the equilibrium between learning and fun, this research contributes to a broader understanding of how to design games that are both accessible and enjoyable for all.
Future studies should explore how this accessibility design model can be improved for disabled users, such as those who are hearing impaired.Expanding the model's applicability to a wider range of disabilities would make it even more impactful and relevant in the feld of educational game design.In addition, accessibility design can be enhanced with technologies such as artifcial intelligence (AI) and augmented reality (AR).AI can be used to provide adaptive gameplay experiences tailored to individual needs, while AR can create immersive and interactive learning environments.
Evaluating serious games is crucial in determining their efectiveness and impact, and further studies could be conducted using standardized evaluation and assessment methodologies for serious games.Future studies can focus on creating and refning these evaluation tools, enabling researchers and educators to consistently measure the impact and educational outcomes of such games.
Te limitation of this research is that the sample size was relatively small.Tese limitations should be taken into account in future research.Researchers can consider expanding the study to a larger and more diverse group of participants, including low-vision children from diferent age groups and backgrounds.

Figure 2 :
Figure 2: Te conceptual model of accessibility in serious games for low vision.
the game should be diferentiated, whether correct or wrong, with audio or visual feedback Storyline 80 Provide an introduction to the characters in the game Te topic and subtopic should be presented in the learning contents (ii) Te number of mathematical tasks should be increased, and the task design should be improved 14 Advances in Human-Computer Interaction

Table 1 :
Te analysis of accessibility elements from previous accessibility models and frameworks.

Table 2 :
Accessibility elements for serious game.Te user interface should be simple to reduce children's cognitive load and easily adapt to low-vision children Navigation (i) Te menu design should be simple, with a start menu and an audio button so that users can navigate the game easily Dialogues, menus, and tasks should be incorporated with sound recordings (iii) Low-vision children can only focus on one sound at a time.Terefore, instructions should be included with audio (iv) Te task can be repeated if the low-vision children require it (v) Sound is used as an accessibility element and is important for vision problems (vi) Audio instructions must be clear.Sound recordings are incorporated in dialogues, menus, and tasks (vii) One sound should be played at a time because low-vision children can only focus on one sound at a time (viii) Instructions should be provided with audio (ix) Te font size should be 18 or more and should use the serif font (x) Tere should be high contrast among fonts, graphics, and backgrounds, and the graphics should be bigger Language (i) Use simple language that low-vision children can understand Interactivity (i) Use simple interaction between children and the game 4 Advances in Human-Computer Interaction educational component of games can enhance the learning experience

Table 3 :
Analysis of the game model and framework for education (game).

Table 4 :
Analysis of the game model for education (pedagogy).

Table 5 :
Te elements of universal design.

Table 6 :
Te children's technology principle.Te dragging movement must be done by clicking on the object to attach it to the pointer and then clicking again and releasing it to the desired location (iv) Te interface should not cause children to hold the mouse button for a long duration

Table 9 :
Summary of responses from experts for accessibility.Te experts stated that the game informed users on what was going on using proper multimedia feedback.Te game provided multimedia feedback for users' actions because the title on the screen describes the contents and game status.can understand the multimedia feedback easily

Table 10 :
Summary of responses from experts for game design.

Table 11 :
Summary of responses from experts for pedagogy.Te experts were satisfed with the learning objectives because they were clear.Tey also found that the learning activities were interesting, and the game assisted users in learningLearning theory Te experts agreed that the learning activities were interesting.Te game can support self-learning and learning medium through activitiesLearning contentsTe game contents were acceptable.Te contents were clear, simple, and easy to understand.Tus, players will be able to understand the learning goals Advances in Human-Computer Interaction

Table 12 :
Summary of usability percentage and improvement comments.Improve the text size for the name of the game