1. School of Computer Science and Engineering, Northeastern University, Shenyang, China
2. School of Software, Dalian University of Technology, Dalian, China
3. China Telecommunication Technology Laboratory, China Academy of Information and Communications Technology, Beijing, China
4. School of Mechanical Electronic and Information Engineering, China University of Mining and Technology (Beijing), Beijing, China
5. Department of Game Design, Faculty of Arts, Uppsala University, Visby, Sweden