Raketmatte is an App designed to enhance children’s numerical magnitude. This study describes the agile process behind the scene from the making of the App. The focus of the app is the transition from a logarithmic to a linear view on the mental number line. Theoretically the app is based on the integrated theory of numerical development, and the app aims to train the users mental number line. The study also describes how elements from gamification has been incoroprated in the final product.