## 2 Background Work
### VR as a Medium in Cultural Heritage  
One of the main characteristics of VR is that headsets completely take over users' vision to give the impression that they are somewhere else. For games, VR supersedes the surroundings, taking the user to other places where physical presence is no longer important. These features provide numerous possibilities for VR games in cultural heritage, as the player is free to travel to different locations (real or fictional) across time and space and have experiences from different historical or even future eras. Dealing with VR, one inevitably deals with immersion, the feeling of being a part of the virtual environment. Although immersion is present in other mediums too, such as books and films, VR immersion is not only mental but could be also physical. In this case, the feeling of being physically present in the virtual world is strong, of course depending on the quality of the VR environment and its design [16]. However, the effective reconstruction of the virtual world for cultural heritage VR games is a challenge. Significant historical knowledge is needed in order to reconstruct past worlds in ways that are meaningful for the player and to allow her to play and explore history. Details on the appearance of monuments, objects, people, landscapes, etc., are very important in creating the right interaction conditions for the game [17]. In this sense, AR games for cultural heritage might be easier to implement than VR ones, as AR uses a real world setting while VR needs to reconstruct entire worlds. In addition, AR might only need a smartphone for its use, whereas VR needs a headset device. VR in cultural heritage is often combined with storytelling such that the effects of both VR and storytelling are maximized. In this setting, the person is using multiple modalities to access information, as she experiences the place where the story is evolving in the virtual world [18]. For example, iMareCulture explored ways storytelling, VR games, and underwater archaeology could be combined, as players could explore cities long lost under the sea (while playing in VR) [19]. Moreover, VR applications for cultural heritage can take many forms. Apart from games and reconstructions of different spaces, VR can be used in different and even unexpected forms of culture such as poetry [20], and researchers appear to be testing the medium and exploring its full potential. VR can also be used for testing research hypotheses, like assisting archaeological research. For example, VR and 3D models were used to explore architectural history and features of buildings that no longer exist [21]. For the development of virtual worlds and games for Cultural Heritage, different techniques are used. In the case of the historic Klodzko Fortress in Poland's Lower Silesia, terrestrial laser scanning was used to capture the real world. The scans were later used in a game engine to create virtual interactions [22]. The use of game engines for the implementation of virtual cultural experiences and VR culture games is popular with different researchers, since they provide a solution in reducing the production cost of VR applications and also in helping to overcome different technical issues [23]. Gamification of VR experiences is a topic of research that has been particularly increased with the growth of VR technology, such as, low-cost HMDs and high field-of-view. In [24], researchers compared different human-computer interaction methodologies for real-time VR simulation of both tangible and intangible digital heritage sites and the creation of dedicated, immersive, gamified curation experiences. Moreover, various interaction methods, such as sensor-based, device-based, tangible, collaborative, multimodal, and hybrid interaction methods, have also been employed by immersive reality technologies to enable interaction with the virtual environments. Previous studies compare the existing VR technologies and interaction methods against their potential to enhance cultural learning in Virtual Heritage applications [25].