## 6 Conclusions  
This study shows that rethinking the public space design process from an analog 2D design (created by one professional designer) to a 3D digital co-design environment is possible, although many designers still develop their designs only using paper-based methods. It has been shown that a lack of knowledge among designers, but especially among stakeholders, about 3D digital interfaces and data availability prevents the optimal use of the new tools from the beginning of the design process. Simple digital tools for designing in 3D using controllers instead of a 2D mouse are necessary and readily available. The literature review shows that this requires integrating different expertise in a transdisciplinary context.  
The online questionnaire, which was used to gauge user appreciation for designing in 3D versus 2D, confirmed that there are still some barriers; however, it did confirm that all participants called for greater emphasis on 3D and VR/XR in the aspects of communication, participation, co-creation, and co-design. The complexity of design, (road) safety, transport policy, ecology, sustainability, noise, and user satisfaction, combined with the increasing demand for stakeholder consultation and participation, is leading to a growing need for better graphic representations. All stakeholders, including the designers, greatly appreciated the experiment's online 3D and VR design tools. Real-time animations using VR simulators and the incorporation of designs into 3D city models and digital twins will result in a higher design quality. The same tools and the VR bike also received significantly high ratings for interactive communication from all subjects.  
In the move towards cyber-physical public design between virtual and physical objects, our research experiment has shown that gamification (using VR and online 3D) could play a central role in the participatory 3D co-design of public spaces. The use of a game engine, in which the design and communication processes run in parallel, provides new insights into the design process. Engaging citizens in 3D co-design by using XR and 3D online interactive tools from the beginning and in all subsequent phases of a public space design process can be a game changer. This research shows that after testing these tools, the appreciation is high and the benefits are proven. Further dissemination of the knowledge about the various forms of XR among designers and non-designers is necessary to improve design quality. From a spatial policy perspective, this technology should be promoted.  
**Author Contributions:** Conceptualization, methodology, validation, investigation, resources, writing--original draft preparation, M.M.; writing--review and editing, L.D.C. and L.M.; visualization, M.M.; supervision, K.B., P.D.M. and N.V.d.W.; project administration, M.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the \"Research Foundation--Flanders F.W.O.\" with a \"Special PhD Fellowship\" under grant number 1901421N.  
**Acknowledgments:** The authors would like to express their gratitude to the city of Ghent for the availability of the 3D open data and to [PERSON] for his support during the testing and development. We would also like to thank the internship students [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON]. Thanks also to [PERSON] for linguistic support and [PERSON] (FIRE) for statistical support.  
**Conflicts of Interest:** The authors declare no conflict of interest.