Before proceeding to the design stage, it is essential to conduct a preliminary study to gather information on the following aspects: (1) The functioning of the learning process in schools, (2) Students' awareness of the importance of occupational health and safety, and (3) The requirements of teachers and students for effective learning resources. The present data is founded on the framework of e-learning developmental theory, which is aimed at identifying the conditions of learning, student attributes, initial knowledge of students, and significant learning events that necessitate renewal (Source not found, n.d.).

According to the results of the needs analysis, further to the information shared earlier, there were a few barriers that impeded the progress of developing learning materials. Firstly, the learning media utilized did not meet the eligibility criteria for use, as several students found it challenging to operate. Secondly, many students lacked comprehension of the significance of studying Occupational Health and Safety material. on the other hand, information was also found that only 10.4% of the students use multimedia, while the other 79.6% rely on material summaries through PowerPoint, PDFs, and discussions via WhatsApp during their practicum learning process. The study found that all respondents owned smartphones, and 96.3% of them used smartphones as their learning medium.

This observation shows that there is a potential for developing mobile applications that can integrate teaching materials, modules, learning videos, and practice questions into one mobile application to answer the problems stated above (Source not found, n.d.). During the advanced analysis stage, it was found that both teachers and students require efficient and effective learning media. They referred to mobile applications as a preferable option for learning due to several reasons such as interactive and fun learning media can help students learn independently. Teachers can present teaching materials in an engaging way by combining audio, video, and animation in the application. This approach can raise awareness about the importance of occupational health and safety.

Efficient and effective learning requires the availability of suitable and adaptable learning resources that can be accessed by learners at any time and place (Source not found, n.d.). A medium can be categorized as a learning medium if the tools or techniques used can convey information or messages from educators to students during the learning process (Source not found, n.d.). A mobile application is a type of learning media that satisfies several criteria. It can serve as both a medium and a resource for students (Source not found, n.d.), offering learning materials, modules, videos, practice questions with feedback, games or illustrations, and contextual material (Source not found, n.d.).

Designing Stage After conducting a preliminary study and needs analysis, it was found that students require a mobile application that can combine various learning sources such as text, audio, video and simulations to learn about Occupational Health and Safety before beginning practicum activities. All elements in the application should prioritize student characteristics to display media that can maintain student motivation and concentration levels (De Pace, Manuri, Sanna, & Zappia, 2019). Using this information, the application specifications were formulated during the design stage of the mobile application.

Mobile applications can be developed using the Smart Apps Creator 3 software. This desktop application allows users to create interactive multimedia content with a simple design and layout that is easy to use (Source not found, n.d.)). The application results in APK, .exe, and HTML5 format files, which are compatible with different devices such as computers, laptops, and smartphones (Source not found, n.d.).

During the development stage, the first step is to formulate general media concepts and teaching material concepts. The media concept is created by making flowcharts and storyboards to design the content (Figure 1 & attachment 1). Then, for the formulation of teaching materials, they are arranged based on basic competencies and indicators sourced from SKKNI KEMNAKER No. 38 of 2019 which covers the basics of Occupational Health and Safety and the potential and prevention of hazards in workshops.

To enhance the effectiveness and efficiency of learning materials, it is recommended that they are transformed into learning media devices (Source not found, n.d.). The digitalization of learning 4.0 has necessitated an increased demand for e-learning oriented learning media (Source not found, n.d.). Additionally, the widespread use and rapid development of smartphone technology have made it possible for students to use their devices as a learning tool, allowing them to learn independently (Source not found, n.d.).

The mobile application development consists of five main menus. The first menu is the home page that displays an explanation of the application, navigation for use, and the personal data of the application developer. The second menu is the material page, which contains a selection of materials related to Occupational Health and Safety. The material includes theoretical explanations in the form of text and images. The third menu is the video page, which contains learning videos that include infographics and simulations. The fourth menu is the practice page, which contains several questions to evaluate student learning. Lastly, the fifth menu is the game page, which contains gamification features related to Occupational Health and Safety signs.

The design of the five menus refers to ideal aspects of learning media, such as ease of use, the accuracy of the information, completeness of material, layout, and colors used, supporting illustrations, and game menus as an effort to maintain students' enthusiasm for learning (Source not found, n.d.). The entire development process is related to efforts to improve learning objectives (Source not found, n.d.).

After the prototype is produced, product testing (alpha testing) can begin after validation and assessment from material expert, media expert and practicioners to determine the suitability of the mobile application (Source not found, n.d.). Their expert assessment produces recommendations that serve as a reference for improvements during the product development stage (Source not found, n.d.). The results of the application development can be seen at following figure.

Alpha Test An alpha test is an initial evaluation conducted by experts to assess various aspects such as content, user-friendliness, and product suitability. The primary objective of this test is to identify and mitigate any potential errors in the product before it is made available to students. Additionally, it can also help determine if the product can function optimally.

The table below presents the results of the media expert’s assessment of the product.

The questionnaire is designed to evaluate the suitability of learning media products based on aspects of visual communication, illustrations, and benefits (Source not found, n.d.). To determine the effectiveness of visual communication, the questionnaire assesses the suitability of image selection, color, font selection, and layout. In terms of illustration, the questionnaire evaluates the ease of use, instrument arrangement, material presentation, appearance, and image proportions (Source not found, n.d.).

The questionnaire also includes indicators to assess the benefits of mobile applications, based on their ability to minimize misperceptions and make it easier for teachers to deliver material (Source not found, n.d.). The average score obtained from the assessment of these aspects was 100%, indicating that the product is "very feasible".

Expert assessments of mobile applications are based on two aspects: material content and material benefits. The content of the material is evaluated based on its suitability with basic competencies, concept correctness, image illustrations' suitability and clarity of the material's meaning and function (Source not found, n.d.). On the other hand, the benefits of the material are evaluated based on the indicators that the media can be used as a learning supplement, minimize misconceptions of the material, and facilitate teachers in delivering teaching material (Source not found, n.d.). The results of the material expert's assessment of mobile application products as learning media are as follows.

The average expert assessment of the material of the product was 90.47%. This value indicates that the developed mobile application is “highly feasible” in terms of material aspects. The results expert’s assesment shown in Figure 3.

In addition to expert validation, three teachers from a vocational high school program for Construction and Housing Engineering carried out practitioner validation. This testing was done to confirm the quality of the media and materials used for learning. According to the assessments from the practitioners, the learning media was rated as "very decent/good" with an average score of 92.5%.

This testing is the stage of fully testing a product for students. The results of this testing are an assessment of the function and feedback from students or product users. Once the product is approved by media expert, materials experts, and practiccioner it undergoes testing on users, specifically, students of Surakarta Vocational High School. The testing was conducted on 3 students selected in clusters to represent different ability levels (high, medium, low) in practical learning (Verbraken, Bravo, Weber, & Baesens, 2014). The results of the user test are presented in the table below.

Based on user testing, the mobile application has been rated "very feasible" with an average score of 90%. The application has received positive feedback from media experts, material experts, practiccioner and users. Therefore, it can be used effectively for learning Occupational Health and Safety during practicums (Source not found, n.d.). This effort aims to facilitate optimal student learning. The data paints a positive picture of students' perception of the application under development. Additionally, research indicates that this media has the potential to foster the attainment of learning objectives (Duryan, Smyth, Roberts, Rowlinson, & Sherratt, 2020)and promote awareness of occupational health and safety (Source not found, n.d.). Moreover, the media should offer information that enables students to equip themselves for the workforce, including work safety guidelines, management, and culture within the industry (Source not found, n.d.).

After testing was carried out on users in categories based on ability level, testing was also carried out on one class to obtain information about various aspects of the media, such as ease of understanding and use, presentation of media and material, ease of use, and achievement of deeper learning objectives. This trial involved 28 students from Construction and Housing Engineering at State Vocational School 2 Surakarta. The test results obtained a score of 90.35% which placed it in the "Very Decent/Good" category.

The findings of the alpha and beta testing conducted at Surakarta Vocational High Schools have exhibited positive outcomes in the development of application-based learning media. These learning tools have been designed to facilitate the acquisition of knowledge in the domain of occupational health and safety. The results of the testing indicate that application-based learning media can be an effective aid in enhancing the learning experience of students while augmenting their understanding of safety protocols and measures in the workplace.