The ubiquity of touchscreen, mobile tablet technology has resulted in a plethora of "apps for learning" yet few leverage the learning sciences as a design driver. This paper describes our approach to integrating the learning sciences with best practices in app design: a design framework that involves researchers and developers in a co-development process to create apps based on research and evidence. Our framework centers around a learning blueprint which is intended to serve as a "boundary object." This boundary object facilitates a design process that allows the design team to focus on both children's engagement and learning. Here we describe the challenges that our project team encountered and our approaches to overcome those challenges on the Next Generation Preschool Math (NGPM) project, a development and research effort devoted to creating a supplemental preschool math curriculum supplement with integrated digital apps.