Re-Mission is an action-adventure video game designed to motivate teens and young adults with cancer to engage in appropriate and effective self-care. In the game, players take the role of a nanobot named Roxi who travels through the bodies of young cancer patients to blast their cancerous cells with chemotherapy and to help them manage their disease. To win, players must find and destroy all the cancer cells and administer medications as needed.  This game and six Re-Mission mini-games are available free of charge.  An extensive randomized controlled trial found that the game significantly improved players' cancer-related knowledge, self-efficacy, and adherence to treatment plan.