Patient adherence to medications is crucial for reducing cardiovascular risk after an acute coronary syndrome (ACS). Although causes for low adherence are diverse, forgetfulness and lack of awareness about treatment importance are accountable for many cases. As a result, medication reminder apps have attempted to tackle this problem. In our work, we present the development of an app with gamification mechanisms to foster adherence and to support the behavior change processes of the Health Access Process Approach (HAPA) theoretical framework. To design our intervention, we relied on a user-centric approach. We listed the main factors related to high and low adherence from the Medication Adherence Reasons Scale (MAR-Scale) and identified functionalities that could address it. We focused in particular on forgetfulness, knowledge and beliefs about medication as the main barriers for adherence. We implemented a quiz and storytelling as gamification strategies to help motivate patients complete their medication journal and to maintain adherence on the long-term.