18.12.2023. Human Digital Twins (HDTs) have recently emerged as promising tools for various healthcare applications. However, most applications utilize HDTs as passive data repositories. DTU team explores an alternative conceptualization of HDTs as active, engaging elements in serious games for rehabilitation. They developed a simplified Badminton game with an “HDT Opponent” that mirrors patients’ past performance trends and appearance. An initial user study revealed a promising potential to provide personalized, motivating experiences but also limitations regarding opponent visibility, behavioural perceivability, and motivation sustainment. While only an initial step, this work demonstrates a new application area for HDTs and sets the foundation for future research to explore the full potential of HDT-based opponents in rehabilitation gaming.