Creative burnout, characterized by stagnation, exhaustion, and rigid routines, can hinder creativity and well-being in software development teams. Although widely acknowledged in practice, creative burnout remains underexplored in academic research on software development. This study investigates how playful interaction design can help mitigate creative burnout in Sprint Retrospectives. Using a Design Science Research approach, we developed and evaluated ‘Scrumstinct’, a design artifact for introducing playfulness into retrospective practices, tested in workshops with eight teams across diverse industries. Based on qualitative analyses of pre- and post-session interviews and video observations, we propose six design principles for integrating playfulness to address team-level creative burnout. Our findings show that playful retrospectives can reframe problems, foster openness, and reduce emotional fatigue. We argue that playfulness in agile practices holds the potential to reshape team culture and support sustainable creativity in software development.