As part of developing and researching a virtual reality (VR) game intended to increase access to and broaden participation in STEM learning, designers and researchers from EdGE at TERC and interns from Landmark College, a post-secondary institute for learners with ADHD, autism, dyslexia, and other learning differences, have been immersed in an intensive co-design process. Co-design embraces the ‘nothing about us without us’ movement by ensuring stakeholder voices, in this case neurodiverse learners, have a prominent role throughout the design process. We present our co-design process, key lessons learned, important game-design decisions, and the experiences and perspectives of individual co-design participants. And recommendations are provided to help guide others who are interested in implementing a co-design process of their own.