This document discusses using behavior change strategies in mobile applications. It notes that engagement with an app and targeting a specific behavior, like exercise or weight loss, are related but different goals. The document cautions against coercion and deception in persuasive design and recommends a straightforward approach. It discusses creating engagement through fun, unpredictability, stimulation, mystery, and self-expression without being overly seductive. Delighting and enchanting users through goals, rules, challenges, feedback and experiences of competence can support behavior change when integrated seamlessly and making use and behavior the same thing. Common persuasion strategies are referenced.