The use of exergames in physical therapy has gained prominence for providing greater engagement and motivation during rehabilitation exercises. However, there is still a gap in the literature regarding how to integrate gamification elements within usability and user-centered design principles. This paper aims to analyze this combination and presents the conceptual prototype of the therapeutic game "Toque os Alvos". The methodology consists of a review of gamification and design frameworks to support the game’s conception. Designed for the Meta Quest 3 device using Unreal Engine 5, the exergame focuses on upper limb rehabilitation by stimulating range of motion, motor coordination, and reaction time through virtual target interaction mechanics. The proposal incorporates immediate visual feedback and an adjustable difficulty progression system based on speed, distance, and target size. The study concludes that applying these design principles can enhance treatment adherence and session efficiency, with the next steps being the development of a functional prototype and user testing.