1 Introduction

The online shopping sector has seen consistent growth, driven by the widespread adoption of online consumer culture due to the COVID-19 pandemic (Bhatti et al. 2020). It offers several advantages, including the elimination of physical constraints of time and space, the ease of comparing various products, and the opportunity to make affordable purchases through promotions and coupons (Srivastava and Thaichon 2023; Vivek et al. 2012). In addition, this market’s expansion is not limited to the younger generations accustomed with the online consumption but extends to older demographics in their 50s and 60s, who, despite their traditional offline consumption habits, have shown active participation in online shopping. This broader demographic engagement is driven by their significant purchasing power and specific consumption preferences (Moschis 2012; Kovalenko and Mazaheri 2021).

With the surge in online purchasing and the shift towards contactless shopping, virtual-environment-based services have gained popularity, offering new experiences (Vakulenko et al. 2019). Initially, virtual reality (VR) technology was applied mainly in experiential domains such as exhibitions, theme parks, and entertainment. However, its use has recently, broadened to encompass various sectors, including gaming, education, and shopping (Loureiro et al. 2019; Pizzi et al. 2019). VR shopping stores provide a three-dimensional (3D) shopping experience, allowing users to explore products in a virtual space. Moreover, these platforms offer a highly immersive experience through vivid imagery and sensory experiences, not restricted by the size of a physical display (Speicher et al. 2017; Lau and Lee 2019). This virtual shopping experience enhances consumer trust by offering a comparable shopping experience safely from home, assisting in making purchase decisions. Recently, numerous well-known brands have embraced VR technology to launch shopping content and platforms. These virtual stores allow users to explore and purchase 3D-rendered products without the need to visit physical stores (Speicher et al. 2018). Notable examples include Dolce & Gabbana’s VR boutique (Dolce&Gabbana, 2020), Dior’s VR store (Dior 2020), and, within South Korea, Samsung’s VR store (Samsung 2021), and W-Concept’s VR Showroom (W concept 2021).

These offerings encompass immersive VR environments, where users engage with products using head-mounted displays (HMD), as well as non-immersive VR environments that enable product viewing on smartphones or computer monitors (Mills and Noyes 1999). The latter allows users to engage with a virtual world without specialised device, through monitors or screens, and is widely applied in 3D games and simulations. In contrast, immersive VR involves wearing HMDs, providing a more realistic and engaging experience by isolating the user from the real world.

Despite significant advancements in VR shopping platforms, their development remains in its early stages. In fact, many systems are yet to reach commercial viability (Kim and Ha 2021). A significant challenge lies in the seamless integration of product information and purchasing processes within the virtual shopping environment (Tran 2010; Lau et al. 2013). Several existing platforms have overly focused on the technical aspects of VR content, often compromising with user functionality and satisfaction (Kim and Ha 2021; Tran 2010). Such a narrow focus neglects the critical requirement of prioritizing diverse and user-friendly experiences, particularly in HMD-based virtual shopping stores. This highlights the existing gaps that need to be addressed for these platforms to succeed. In addition, there is a lack of appropriate research on universal design that considers various user groups. Universal design is a strategic approach for creating products, facilities, and services that are accessible to all individuals, regardless of their gender, age, disability, language, and other factors (Story et al. 1998). Thus, to achieve widespread commercialization of VR shopping stores, future research must consider the needs of diverse user groups.

This study aimed to develop a satisfying and immersive VR-based shopping experience that could cater to a diverse range of users, thereby addressing the current shortcomings in existing platforms. Considering that many VR shopping environments have historically prioritized technical implementation over user functionality and satisfaction, this study attempted to bridge that gap by focusing on the holistic needs of users. Consequently, we conducted a comprehensive systematic literature review and an in-depth video ethnography to identify the essential features and user preferences within virtual shopping stores. Following the identification of key features, a prototype of the virtual shopping store was developed. Moreover, an usability test was conducted to further validate the effectiveness of this approach. This process ensured that the design direction aligned with our goal of creating a user-entered and immersive shopping experience. Consequently, these methodologies facilitated the gathering of critical insights into the user experience, which have often been overlooked when designing VR platforms. Based on these insights, this study aimed to inform the design, development, and rigorous validation of an HMD-based universal virtual shopping store that delivered on technical performance while prioritizing user satisfaction and inclusivity. This ensured that the final product offered a truly engaging and accessible shopping experience for all.

Figure 1 introduces the process employed in this study. The remainder of this paper is organized as follows. Section 2 presents an analysis of prior research on virtual shopping experiences, including case studies of virtual stores and discussions on VR accessibility and universal design principles. Section 3 presents an analysis of the shopping experience in physical stores through video ethnography to identify the key features that could enhance virtual shopping stores. Section 4 details the specific features of the universal virtual shopping store prototype developed in this study. Further, Sect. 5 describes the user evaluation process employed to validate the features of the prototype, along with an analysis of the results obtained from the user experience study. Thereafter, Sect. 6 describes the user evaluation process employed to verify universal design features with colour blind people. Section 7 presents a discussion on the implications of our findings. Finally, Sect. 8 concludes the study by summarising the key outcomes.

Fig. 1
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Overview of the research procedure in this study

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2 Literatures and services review

2.1 Prior research on virtual shopping experience

Most existing research on virtual shopping experiences has focused on the virtualization of real stores to create environments. These studies have explored various aspects: (1) consumer behaviour in virtual environments, (2) enhancement of shopping experiences through VR, and (3) brand perception and marketing strategies in VR.

Research on consumer behaviour in VR environments has primarily focused on investigating the similarity of consumer behaviour in VR shopping environments with that in physical stores and consequently exploring whether VR could be used as a reliable tool for consumer behaviour research. van Herpen et al. (2016) compared a physical, PC-based virtual, and PC-based 2D photo stores. They found that consumers in the virtual store exhibited product choices and spending patterns similar to those in the physical store. Moreover, their purchasing behaviour related to product shelf positions (e.g., top, left) appeared to be more natural. Thus, the VR shopping environment effectively replicated the actual shopping experience, thereby highlighting the importance of immersive and realistic virtual environments. Schnack et al. (2019) compared an HMD-based immersive virtual simulated store (VSS) with a desktop-based VSS (Schnack et al. 2019). Participants experienced higher telepresence and more natural interactions in the immersive VSS based on the visual elements, sounds, and interaction with the store environment in VSS. Lombart et al. (2020) compared physical, non-immersive virtual (desktop-based), and immersive virtual (HMD-based) stores. They observed that the consumers tended to purchase more items in the immersive virtual store. Further, they placed greater importance on the enjoyment of the shopping experience in the immersive virtual store. This indicated that such environments could provide a more emotionally satisfying shopping experience. Siegrist et al. (2019) compared a physical supermarket with an HMD-based 3D virtual supermarket. The participants were found to exhibit very similar behaviour in both the virtual and physical stores, with no significant differences in terms of eye movements, information search, and product selection. Ploydanai et al. (2017) compared virtual stores with four different store layouts (long shelves/short shelves, and parallel/non-parallel placement). They found that the shelf arrangement and length in the virtual stores influenced the consumer product exploration and purchasing behaviour. Overall, consumer behaviour in the VR environments has been found to be significantly influenced by immersion, interactivity, and sensory elements (e.g., visual and auditory stimuli). Moreover, the research emphasizes that VR can provide a shopping experience similar to reality.

The existing research on enhancing shopping experiences using VR has primarily explored the manner in which VR technology can amplify consumer experiences in commercial settings. Speicher et al. (2017) developed a system called VRShop, which combined the advantages of both online and offline shopping in an immersive VR shopping environment. This system enabled users to browse and select products using voice input and head movements. Further, the system provided high levels of immersion and usability, thereby significantly enhancing user satisfaction. Voice input was the most efficient and preferred method for product navigation in this case. Moreover, the VRShop system demonstrated the potential to overcome the drawbacks of online shopping while offering the benefits of offline shopping. Thus, it effectively enhanced the shopping experience. Lau and Lee (2019) designed a virtual store called FutureShop using stereoscopic VR (StereoVR) technology. Shopping in the StereoVR environment increased the purchase intentions of consumers. Interactive elements such as music, lighting, and product rotation were found to enhance the positive experience. Further, Peukert et al. (2019) and Meißner et al. (2020) compared high-immersion VR environments (HMD-based) with low-immersion VR environments (desktop-based) to verify the impact of immersion on consumer perceptions and behaviour. Both studies determined that consumers were less price-sensitive and tended to select various products in high-immersion VR environments. In addition, high-immersion VR environments increased the sense of remote presence, thereby positively influencing consumer enjoyment and intention to reuse the system. These studies emphasized the potential of VR technology for revolutionizing consumer experiences in retail. Morotti et al. (2020) integrated the Amazon Alexa voice assistant into a VR environment. They developed an interface that allowed users to browse and purchase products using voice commands. The study found that voice commands provided an accessible method for users, including those less familiar with technology, to engage in VR shopping. This resulted in a more satisfying shopping experience. Shravani et al. (2021) proposed an HMD-based immersive VR supermarket platform that offered personalized recommendations based on the user’s purchase history. Users found the interaction with the 360° rendered stores and products to be more realistic and enjoyable. Further, they rated the recommendation system as useful in aiding purchase decisions. Xi and Hamari (2021) systematically analysed existing studies on VR shopping experiences. They found that VR shopping environments yielded more positive outcomes than traditional shopping environments. Further, they highlighted the crucial role of visual interfaces and interaction technologies. In addition, multisensory technologies, sensory devices, and the presence of other shoppers or salespeople were found to significantly influence the consumer perceptions, judgments, and behaviours in VR environments. Thus, these studies suggest that VR environments can offer a differentiated customer experience through personalized recommendation systems, product customization, and interactive features, thereby providing a competitive edge over traditional shopping experiences.

Finally, the existing studies on brand perception and marketing strategies in VR have primarily explored the ability of VR to enhance the interaction between brands and consumers and optimize marketing strategies. Altarteer et al. (2016) developed a semi-immersive VR System designed to enhance product visualization and customization experiences in online shopping environments. This system facilitate users in rotating and zooming in on 3D models using hand gestures. Compared to a 2D static image system, the VR system received significantly higher ratings in terms of the customization experiences, perceived experiential value, and attitudes toward the system of the users. Thus, VR technology can significantly enhance the consumer experience in the online product customization process for premium brands. Moes and van Vliet (2017) found that VR could effectively virtualize the shopping experience of physical stores, thereby enhancing consumers’ positive perceptions. The study compared three types of visual materials in the context of a fashion store background (a standard static photo, a desktop-based 360° photo, and an HMD-based VR photo). Participants who observed the VR photo had the highest levels of store visit intention, purchase intention, and positive perceptions of the store. Further, Pizzi et al. (2020) demonstrated that VR stores could induce consumer behaviour similar to that in case of physical stores and enhance store satisfaction through increased immersion. In particular, the perception of product arrangement size was crucial to improving satisfaction with the VR store. Kang et al. (2020) showed that interactivity and visual-spatial cues in 3D VR stores positively affected the product evaluations and purchase decisions of the consumer. Further, the study also emphasized that interfaces providing sufficient information, rather than simply being playful, could more effectively increase the purchase intentions of the consumers. Thus, these studies highlight that VR technology can be a powerful tool for enhancing brand perception and strengthening consumer interaction. In particular, VR has demonstrated potential in terms of increasing brand value and providing immersive experiences for consumers, particularly in case of the luxury brand and fashion industries.

2.2 Analysis of commercial services

In our study, we conducted a case analysis to identify key shopping features that enhance user experience by analysing commercially available content from virtual shopping stores. Our selection process involved online searches with keywords such as ‘VR Shopping Mall’, ‘VR Store’, and ‘VR Showroom’, focusing on instances that offered both immersive and non-immersive VR environments. Upon determination, the target commercial shopping stores comprised those for which information could be obtained from websites, brochures, and real-world applications. We analysed four distinct cases: Samsung VR Store, Mandarina Duck VR Digital Showroom, W-Concept VR Showroom, and Dolce and Gabbana VR Boutique. Our examination covered the shopping environment, interface design, and specific shopping-related features of each (Table 1).

Table 1 Analysis of virtual shopping store contents
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The results indicated that most virtual shopping platforms offered onscreen buttons for seamless movement coupled with a mini-map for quick navigation. These platforms were accessible via web, mobile, and HMD devices, and they operate from a first-person perspective. Consequently, users could access fundamental product information and links to official online stores for further details. Although apparel items were verified through model-worn photos, certain accessories were often limited to simple images. This rendered the assessment of the details challenging. This highlights the importance of direct interaction features, such as product zooming and rotation, for a more thorough review. In addition the potential for avatar-based virtual fitting was further recognized as the key to enhancing product engagement. Although innovative, these virtual shopping stores are still in development, owing to a lack of comprehensive shopping functionalities and consistency in design, thereby leading to varied user experiences. Thus, continued research is needed to refine their functionality, interfaces, and interaction designs to ensure satisfying user experiences.

2.3 Virtual reality (VR) research considering accessibility and universal design aspects

Universal design is a strategic approach to creating products, facilities, and services that are accessible to all individuals, regardless of their gender, age, disability, language, and other factors (Story et al. 1998). In the context of VR, research on universal design remains limited, predominantly focusing on accessibility features designed specifically for individuals with disabilities. Accessibility entails the creation of information and communication devices and services that are easily usable by everyone, regardless of any disabilities they may have (Wegge et al. 2007; Kim and Park 2020; Kim and Han 2017). Although universal design incorporates accessibility, it differs by including a broader range of user groups (Iwarsson and Ståhl 2003; Lee et al. 2023).

Research in the realm of accessibility, especially for visually impaired individuals, has predominantly focused on designing UI with accessibility in mind or developing prototypes that applied specific accessibility features (Teófilo et al. 2016, 2018b; Hoppe et al. 2020; Craddock 2018). This includes efforts to improve the accessibility of VR technologies, with studies targeting enhancements in accessibility (Powell et al. 2020; Tariq et al. 2018; Ghali et al. 2012). Individuals with low vision, colour blindness, and blindness. Teófilo et al. (2018a, 2018b) assessed the effectiveness of accessibility features for visually impaired individuals in VR environments. Their work involved testing an open-source solution named gear VRF accessibility, designed to implement features such as zooming capabilities, colour contrast adjustments, automatic reading (via screen readers), and captions within a VR environment (Teófilo et al. 2018a, 2018b).

Moreover, significant efforts have been made to develop prototypes that integrate accessibility features (Luangrungruang and Kokaew 2018; Mirzaei et al. 2012, 2020; Teófilo 2019; Teófilo et al. 2018a, 2018b; Glasser et al. 2019; Jain et al. 2021). Teófilo (2019) proposed an accessibility service tailored for live VR theatres to accommodate individuals with hearing impairments. This service leverages automatic speech recognition, sentence prediction, and spell-checking technologies to generate both text and sign language captions. The efficiency of this innovative system was validated through both quantitative and qualitative research, yielding high satisfaction levels among participants with hearing impairment (Teófilo 2019).

Accessibility research related to individuals with physical disabilities has focused on identifying and addressing accessibility issues encountered during device use (Hong et al. 2017; Mott et al. 2020; Ferdous 2017). This area of paper includes the development of prototypes tailored for individuals with physical disabilities, with particular attention to voice command functionalities (Gerling et al. 2020; Hepperle et al. 2019; Monteiro et al. 2021; Murad et al. 2018, 2019). Mott et al. (2020) discussed methods for making VR systems more accessible to individuals with mobility impairments, emphasising the importance of understanding the varied experiences of individuals with diverse abilities (Mott et al. 2020). Gerling et al. (2020) embarked on designing and testing a VR game specifically for wheelchair users, exploring their preferences and requirements. The findings underscored a keen interest among wheelchair users in VR gaming, highlighting the need to account for disability perspectives, overcome socioeconomic barriers related to technology access, and devise adaptive, flexible VR interactions catering to body diversity (Gerling et al. 2020).

In addition, certain studies broadened the scope beyond specific disabilities, aiming to assess and enhance VR accessibility more generally (Loch et al. 2019; Lischer-Katz and Clark 2021; Cook et al. 2019; Fussell et al. 2019). Prominent companies such as Microsoft, Roblox, W3C, and Oculus have presented accessibility guidelines that cater to a wide range of disabilities, setting a benchmark for inclusive design practices (Microsoft 2023; Roblox 2023; W3C 2021; Oculus 2022).

Based on relevant literature and industry guidelines, we compiled a list of key accessibility features tailored for different disabilities, including visual, auditory, and motor impairments (Table 2). This compilation is based on features that were consistently mentioned across three or more sources or identified as essential components within existing VR technologies. The ‘General’ category of user types outlined in Table 2 encompasses universal features designed without restricting to any specific disability type, reflecting a comprehensive approach to ensuring VR accessibility.

Table 2 Key accessibility/universal design features derived from prior VR technology studies
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3 Analysis of offline shopping experience using video ethnography technique

With the aim of building a satisfactory VR shopping environment, this study observed the offline shopping experiences of consumers. This is because a previous study found that the shopping behaviour of consumers in supermarkets in offline and VR environments was similar (Siegrist et al. 2019). To understand user shopping behaviours and experiences in offline retail stores for prototype development, we employed video ethnography. This method involves recording and analysing user behaviours and interactions with products in their natural environment through video recordings (Zeisel 1984). It is a well-established research method for observing and analysing participants (Yoo and Pan 2013).

3.1 Participants

The study involved a sample of six university students, with an average age of 24.3 (SD = 0.5), comprising three males and three females. Participants were selected based on their good physical health, ability to participate in the experiment without difficulty, and recent experience with clothing shopping within the last three months. Four of the participants reported purchasing clothes at least once a month, while two did so at least once every two months.

3.2 Methods

The experiment took place in a large clothing store featuring mannequins and display tables. At the outset, participants were briefed on the purpose and methodology of the video ethnography. They were then allowed to browse the store freely, engaging in a natural shopping process by selecting clothes they liked and placing them in shopping bags (Fig. 2). This process was video-recorded -recorded by the experiment facilitator. Following the shopping activity, a brief interview was conducted to gather insights on key factors influencing their shopping experiences, their shopping habits, and the motivations behind their selections. The experiment lasted approximately 13 min in total, with participants given the flexibility to take breaks or terminate the session at any time as per their comfort.

Fig. 2
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Experimental environment. The participants freely shopped at the shopping store

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3.3 Data analysis and results

The analysis of the offline shopping experiences, based on the video recordings, revealed that participant behaviours encompassed four distinct tasks: time spent exploring products on hangers, mannequins, and desks, and time spent moving to explore products. We organised the duration spent on each task and analysed the overall shopping time (Table 3). Additionally, we delved into the characteristic shopping experiences, including patterns of user movement and approaches to offline shopping.

Table 3 Average time taken for each task
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Analysis using video ethnography revealed that navigation was accounted for 28.8% of the total shopping time, indicating that a significant portion was dedicated to moving around. This frequent exploration of various stores or navigating spacious stores to find desired clothing items resulted in product exploration times being highest for hangers, followed by desks and mannequins. The majority of time, specifically 57.4%, was spent at hangers, mainly due to tangled clothes, which complicated the process of identifying desired items and their information. Conversely, desks, where items were more openly displayed, accounted for only 9.7% of the time, facilitating easier identification by participants. Mannequins, requiring the least time at 4.1%, saw minimal interaction beyond brief glances, contributing to the shorter time spent on this shopping aspect.

3.4 Derivation of shopping functions for virtual shopping stores

The findings underscore the importance of displaying products using hangers, mannequins, and desks in developing a virtual shopping store that accurately mirrors real shopping experiences. Participant feedback on each of the four tasks in Table 3, guided the identification of necessary interactions for a virtual shopping store, followed by an analysis of essential shopping-related features, as presented in Table 4.

Table 4 Key comments and derived necessary features
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4 Development of universal virtual shopping store prototype

The design and development of the virtual shopping store prototype were achieved using Adobe XD and Unity. The completion of the prototype development is presented in Fig. 1. The prototype feature development phase incorporated insights from existing virtual shopping stores (Sect. 2.2) and observations made via video ethnography (Sect. 3). This facilitated the extraction of user experience-focused shopping features (Sect. 4.1). Further, a literature review on VR content accessibility (Sect. 2.3) facilitated the identification of essential universal features (Sect. 4.2), which shaped the prototype’s design based on a universal approach (Sect. 4.3).

4.1 Derivation of shopping store features considering user experience

Drawing from the features of existing virtual shopping stores discussed in Chap. 2.2 (Table 1) and the essential features identified in Chap. 3 (Table 4), shopping-related features were conceptualised to enhance user experience, guiding the development of the prototype. Key features developed include two navigation functions—teleportation and mini-map warp movements for exploration—and three product manipulation functions: checking detailed product information, confirming product designs, and enabling virtual fittings with avatars (Table 5).

Table 5 Key features of developed virtual shopping store
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4.2 Derivation of shopping store features considering Universal Perspective

From a universal design perspective, this study identified and developed essential features for a virtual shopping store. Drawing on accessibility features identified in Chap. 2.3 (Table 2), two critical universal features were derived for the system (Table 6), which are ‘Voice guidance’ and ‘Tutorial’. ‘Voice guidance’ converts visually displayed information into auditory information, providing auditory feedback and reading content aloud, enhancing accessibility for users. The ‘Tutorial’ feature provides comprehensive instructions for navigating and utilising the content and platform, especially beneficial for users new to VR content and controls, covering controller operations, map configurations, and other essential information.

4.3 Prototype design considering universal perspective

The prototype’s design also incorporated a universal perspective (Table 6), incorporating design elements such as colour changes and high contrast, menu and button design, visual cues for different product types, and central interface placement (Fig. 3).

Table 6 Key design elements of virtual shopping store considering universal design perspective
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Fig. 3
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Example of interface design for universal virtual shopping stores

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4.4 Final prototype development

The final prototype encompasses functionalities identified in Tables 5 and 6, including a tutorial, user location/orientation control (teleportation and mini-map warp movement), virtual fitting using avatars, voice guidance, and an intuitive UI for different product types (hanger, mannequin, desk). These features facilitate detailed product information review and product design confirmation. An example of the final prototype design is illustrated in Fig. 4.

Fig. 4
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Representative screen of universal virtual shopping store prototype.

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5 Usability test for verifying shopping store features

The virtual shopping store prototype was validated, incorporating a subjective satisfaction assessment of the implemented features. This process involved evaluating users’ subjective satisfaction and conducting in-depth interviews to capture detailed information on users’ actual concerns and needs. The study was ethically approved by the Kwangwoon University Bioethics Research Board (Approval No: 7001546-202201202-HR(SB)-011-04).

5.1 Participants

The participant group consisted of 30 adults in their twenties, sourced from a university community, with an average age of 23.3 years (SD = 1.8), including 14 males and 16 females. Of these, 21 had experience with VR devices, whereas nine were newcomers. Additionally, 21 participants were identified as frequent clothing shoppers, with a majority (22) favouring online shopping for its convenience, ease of reducing physical fatigue, and the ability to quickly compare offerings from various stores.

5.2 Procedure

Participants were briefed on the experiment’s purpose and procedures before providing demographic information and signing a consent form. They were introduced to the universal virtual shopping store prototype developed for this study, along with the scenarios they would navigate using the prototype. Using a HMD, participants engaged in virtual shopping tasks, as outlined in the given scenarios. The experiment was conducted using Oculus Quest 2. Participants viewed the prototype displayed in the virtual environment and consequently performed inputs using the controller (Fig. 5). The experimenter observed the actions of the participants in the virtual world on a 32-inch Samsung touch monitor (HDL-T320-OV-IR). Further, the VR space for the experiment was created employing the Unity engine (version: 2021.3.10f1). Scenarios used in the experiment are in Table 7. Upon completing all scenarios, participants completed a subjective satisfaction survey focused on the prototype’s functionality and interface design, and also took part in in-depth interviews. Satisfaction levels were measured on an 11-point scale, ranging from 0 (Not satisfied at all) to 10 (Very satisfied). The experiment lasted approximately 30 min, with participants having the freedom to take breaks or end the session as needed.

Fig. 5
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Experimental environment for evaluating user experience in virtual shopping stores

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Table 7 Scenarios considered in the experiment
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5.3 Results

The experimental results were analysed using descriptive statistics, presenting the subjective satisfaction scores and insights from in-depth interviews related to the universal virtual shopping store in Table 8.

Table 8 Subjective satisfaction results for developed universal virtual shopping store
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The usability evaluation revealed that the prototype received high satisfaction scores across all evaluated factors. The ‘Tutorial’ feature received a score of 8.91 (SD = 0.89) within the shopping function category, while ‘Colour changes and high contrast’ achieved the highest satisfaction score of 9.34 (SD = 0.94) in the universal design category. These results underscore the positive impact of incorporating a universal design perspective on user experience. Furthermore, the overall satisfaction score for the universal virtual shopping store was notably high at 8.13 (SD = 1.34), indicating that the prototype developed in this study successfully met and possibly exceeded user satisfaction expectations.

6 Usability test for verifying universal features

Six individuals with colour vision deficiency were additionally recruited for the purpose of verifying only the universal design features of the developed prototype. This process involved the evaluation of the subjective satisfaction of users and conduction of in-depth interviews regarding the universal design features. This study was conducted based on an ethical approval granted by the Kwangwoon University Bioethics Research Board (Approval No: 7001546-202201202-HR(SB)-011-04).

6.1 Participants

The experiment was conducted with six male participants in their 20s (mean age 23 years, SD = 2.5). They were recruited through a university community. During recruitment, participants were selected based on the results of a colour vision deficiency test, which was conducted using a free online colour blindness test site. Among the participants selected, four exhibited deuteranomaly (a type of red–green colour blindness wherein the green cones are deficient), and two exhibited protanomaly (a type of red–green colour blindness wherein the red cones are deficient). Protanomaly involves difficulty in perceiving red hues owing to a lack of red cones. Whereas, deuteranomaly involves difficulty in perceiving green hues owing to a lack of green cones (Simunovic 2010). Three of the participants had prior experience using VR devices. In addition, five participants frequently engaged in clothing shopping. Among them, online shopping was the most preferred method for four participants; this may be owing to its convenience, time-saving nature, and easy accessibility.

6.2 Procedure

This experiment was conducted in a manner similar to that described in Sect. 5.2. The participants used the developed prototype with an HMD. Following its usage they completed a subjective satisfaction survey on the interface design, followed by an in-depth interview.

6.3 Results

The subjective satisfaction scores and in-depth interview results for the interface design of the developed universal virtual shopping store are presented in Table 9.

Table 9 Subjective satisfaction results when using the interface design of the developed universal virtual shopping store
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The usability evaluation results for participants with colour vision deficiency indicated that the developed prototype received high satisfaction scores across all factors of universal design. In particular, the “Central interface placement” received the highest satisfaction score of 9 (SD = 0.89). Further, the overall satisfaction score for the universal virtual shopping store was high (8.67) as well (SD = 1.21). Thus, these results indicated that the interface design of the universal virtual shopping store developed in this study could provide a positive user experience for individuals with colour vision deficiency.

7 Discussion

7.1 Key features of virtual shopping store for satisfactory user experience

Analysing offline shopping experiences through video ethnography revealed that users often experienced fatigue from the considerable time spent moving around. Perfect exploration time notably varied, with hangers, desks, and mannequins being explored in descending order of time spent. The most time was spent at hangers mainly due to difficulty in disentangling clothes, leading participants to desire easier access to size, price, and material information. Desks, however, facilitated quicker understanding as items were openly displayed, allowing for thorough inspection through rotation. Mannequins required the least amount of time, typically used for quick fit checks and style references. A notable behaviour was the frequent lifting and turning of products for product examination, indicating a desire to assess product suitability. From these findings, key shopping and universal design features were derived to enhance the user experience within a virtual shopping store, leading to the development of a universal virtual shopping store. This mall includes major features such as tutorials, avatar-based virtual fittings, user location/orientation control, voice guidance, and an intuitive UI for different product types (hanger, mannequin, desk). Usability studies showed high overall satisfaction for all features, except for the ‘Voice guidance’ function, with many participants expressing interest in future use if further development occurs.

Concerning ‘Voice guidance’, many participants found discomfort with continuous auditory feedback during navigation and selection, suggesting a preference for optional use. This feedback is consistent with Sikström et al.‘s (2016) study, which indicated that auditory feedback in VR shopping environments does not significantly impact the shopping experience (Sikström et al. 2016). Therefore, an option to toggle this feature on or off would be beneficial, particularly for older individuals or those with visual impairments.

The ‘Tutorial’ feature received the highest satisfaction scores, with feedback indicating its intuitive explanations were helpful even for VR novices. This aligns with Fussell et al.‘s (2019) study, emphasising the importance of tutorials in building confidence and comfort in VR usage through VR tutorials (Cook et al. 2019). Given the limited mainstream adoption of HMDs, providing tutorial features is essential for enhancing user satisfaction with the VR shopping store experience.

The ‘User location/orientation control’ feature, especially teleportation and mini-map warp movements, was well-received, enable efficient navigation to desired locations. while teleportation was favoured for its ability to provide location awareness, initial difficulties with controller manipulation highlighted the need for clear instructions and practice, especially for those new to VR. Additionally, incorporating a joystick-based walking feature could offer a more familiar navigation method for users accustomed to traditional movement controls.

7.2 Reflection on universal design perspective

The interface design of the developed universal virtual shopping store incorporates colour changes and high contrast, intuitive menu and button design, central interface placement, and visual cues for identifying different product types. During the user evaluation, the majority of participants expressed overall satisfaction with the interface design.

The aspects receiving the highest satisfaction scores were the ‘Colour changes and high contrast’ and ‘Central interface placement’. Participants particularly noted that the ‘Colour changes and high contrast’ design quickly captured their attention and was perceived positively due to its dramatic colour contrasts. This observation is supported by the research of Teófilo et al. (2018a, 2018b), indicating that colour contrast significantly influences user satisfaction and readability (Craddock 2018). In our study, a brightness contrast ratio of at least 4.5:1 between text and background was employed, proving satisfactory for both older adults and individuals in their 20s.

As for the ‘Central interface placement’, feedback from interviews indicated that positioning elements centrally was effective in minimising the need for extensive head movements, thereby reducing the likelihood of motion sickness and dizziness. In this prototype, most menus were strategically positioned within a comfortable viewing range for users, approximately − 77 to + 77 degrees horizontally and − 12 to + 20 degrees vertically from the centre point (Alger 2015). This ergonomic consideration is critical for ongoing development of virtual shopping store.

The implementation of visual cues for distinguishing between different product types also garnered positive feedback, with interviewees highlighting the strategic placement of these cues at the top of the products to avoid overlap with other items. This design choice made it easier for participants to quickly notice and identify the products they were interested in, supporting the findings of Glasser et al. (2019) on the effectiveness of visual cues in target identification (Glasser et al. 2019). In this study, a combination of text and icons was used to design these visual cues, confirming their effectiveness in aiding users in identifying desired items.

The universal virtual shopping store prototype developed in this study significantly reduced physical fatigue by allowing users to virtually visit stores and observe products. This virtual environment combines the advantages of online shopping—such as detailed exploration of stores and products via teleportation and mini-map warp movements, and quick viewing of various products through product confirmation features—with the benefits of offline shopping, including trying on products using an avatar that resembles the user and checking product details through an intuitive UI for different product types. Essentially, this universal virtual shopping store combines and enhances both online and offline shopping experiences, potentially enhancing engagement with products and increasing the reliability of purchases. Furthermore, the incorporation of universal design principles and features aims to deliver positive experiences not only for individuals with disabilities and older adults but also for the general users, underscoring the inclusive nature of this development.

7.3 Recommendations

We present a few recommendations for practitioners in the VR and online retail sectors. First, to provide intuitive experiences for diverse user groups, the universal design principles must be incorporated into the features and interface design. Among the key features proposed in Table 5, the teleportation movement and mini-map warp movement features should be developed not only for virtual shopping stores but also for various VR prototypes that require navigation tasks. Additionally, the universal design elements proposed in Table 6 should be applied to the prototypes of all environments (e.g., healthcare, education, gaming, etc.), including virtual shopping stores. As mentioned earlier, accessibility and universal design target different user groups, so it is crucial to carefully consider which user group to focus on when designing prototypes. Second, to maximize the immersion in VR shopping stores, avatar customization and product interaction must be developed further. By enhancing avatar customization, users can not only personalize their virtual presence but also engage in more lifelike interactions, such as trying on virtual clothes or accessories that reflect their actual size, body type, and style preferences. In fact, as shown in Table 8, many participants expressed that they greatly enjoyed trying on clothes with their avatars. Product interaction, on the other hand, allows users to inspect products in 3D, rotate items, zoom in on details, or simulate the functionality of items like gadgets or appliances. This feature brings an added layer of tangibility to the shopping experience that is often lacking in online platforms. Finally, VR shopping stores should integrate and expand upon existing online and offline shopping experiences to better support users in making informed purchasing decisions. This study recommends that at least a mannequin, desk, and hanger be provided to offer an experience similar to offline shopping. Together, these developments would replicate key aspects of physical shopping, enabling users to experience a more realistic and immersive shopping environment.

7.4 Limitation

This study is considered significant owing to the development of an HMD-based universal virtual shopping store followed by the evaluation of the user experience. However, there are several limitations to be overcome. First, the video ethnography method was conducted with a small sample of six participants in a single shopping store. This indicates a lack of representativeness. Generalizing the design based on such a limited participants number and shopping environment is challenging. Thus, in this study, we derived shopping store features by considering various commercial VR store contents coupled with the results of the ethnography analysis. Second, the subjective satisfaction scores employed in the usability evaluation of the universal virtual shopping store prototype were difficult to compare directly with other virtual UX studies. Moreover, the possibility that participants may have felt social pressure to give high scores must be considered, knowing that they were being evaluated and the prototype was developed by the researchers. Third, the universal design part developed in this study was insufficiently verified. We recruited six colour-blind individuals to assess the universal design factors (Table 9), resulting in a high subjective satisfaction score. However, the sample size was small, and we only considered a specific user group. While it is generally accepted that statistical comparison analyses typically require around 20 participants, some research suggests that identifying severe usability problems can be achieved with as few as five participants (Lewis, 1994). In this study, statistical analysis was not deemed necessary; thus, we conducted experiments with six colour-blind individuals. To enhance the generalizability of the universal design aspects, future studies should recruit at least five participants and focus on a more diverse participant pool, particularly including elderly individuals. The elderly are a significant user group in the context of universal design. However, it is crucial to approach VR prototype evaluations for this demographic with caution, as many elderly individuals may have little to no experience using VR technology. This consideration is part of the reason we focused solely on colour-blind participants in this study. Finally, the VR prototype developed in this study was created with the utmost effort, but it may not fully represent commercial VR shopping malls. Participants were made aware of this limitation during the experiment, but there could still be a gap between our prototype and real-world applications. Additionally, the quality of commercial VR applications can vary significantly. Since we did not sample or analyse every available application, this study has clear limitations when it comes to generalizing the findings. Differences in rendering quality and potential side effects like motion sickness in other applications should be taken into account. Therefore, the results of this study should be interpreted cautiously, considering these limitations.

8 Conclusions

Building on the analysis of existing commercial virtual shopping stores and results from users offline shopping experiences captured through video ethnography, this study delineates key shopping functionalities essential for virtual shopping stores. Additionally, by reviewing literature on VR accessibility and universal design principles, it identifies main universal functionalities for virtual shopping stores, culminating in the design of a universal virtual shopping store interface. The prototype of this HMD-based universal virtual shopping store incorporates features such as a tutorial, user location/orientation controls (including teleportation and mini-map warp movements), avatar-based virtual fitting, voice guidance, and an intuitive UI tailored for various product displays (hanger, mannequin, desk). For the universal interface design, it introduces meticulously designed menus and buttons, colour changes and high contrast for greater visibility, strategically placed central interface, and visual cues for different product categories. The evaluation of user experience with the prototype’s features and interface design yielded high satisfaction levels across both shopping-specific and universal functionalities, as well as the overall design approach. Users expressed a strong willingness in exploring the prototype further in the future.

Future research should focus on the further validation of the results of this study across diverse user groups to enhance generalizability. This involves conducting rigorous A/B testing with a greater number of participants and varied shopping environments to compare the developed features and designs with existing commercial VR shopping stores. Moreover, to provide more practical insights into VR shopping platforms, the feedback from industry practitioners must be appropriately incorporated. Gathering input on implementable features and improvements for both online and offline retailers can facilitate the creation of more practical guidelines. Moreover, standardized UX metrics must be introduced in the evaluation process to ensure the objectivity of the results. In this study, subjective satisfaction was assessed by collecting feedback on the features derived in Tables 5 and 6, as well as on the universal design aspects. However, if a comprehensive UX metrics, such as the Computer System Usability Questionnaire (Lewis 1995) or the System Usability Scale (Brooke 1996), had been employed, it would have facilitated easier comparison and analysis of results with future studies. This standardization would provide a more robust framework for evaluating usability and enhance the validity of our findings within the broader research context.

The outcomes of this study provide a robust foundation for future research in virtual shopping store development, highlighting essential considerations for the design and evaluation of content and platforms within virtual shopping stores.