The MyREADY Transition CHD App for adolescents with Congenital Heart Disease (CHD) is designed to educate and empower youth as they prepare for transition from pediatric to adult care. This version is intended for participants to the READYorNot[TM] CHD Trial (NCT04463446) who will require an access code from the Clinical Research team. Participants of the study are between 16 and 17 years of age and have CHD. Its gaming approach in the form of a Journey in the City with a mentor (virtual coach) that helps the user to navigate the buildings, sequentially introduces the educational sections designed to enhance education and medical information management as well as social skills to enable self-management in preparation for adult health care systems. The content of the App is composed of messages, texts, quizzes, videos, as well as skill-based-achievement challenges. The App uses pop-up features to manage reminders aimed at keeping engagement and ensuring adherence to the mApp along the 20 sections of training curricula.