Designing curriculum-based learning activities involves identifying and implementing affordances that provide opportunities for students to engage in actions directed at achieving specific learning objectives. These affordances may be mediated by information and communication technologies (ICT) or traditional resources, peers or teachers, or other contextual features of the learning environment. The learning objectives guide the designer's choice of affordances, whose deployment on specific artifacts is based on assessing the available artifacts' mediating capabilities. Such a design approach puts high demands on the designer's technological, pedagogical and content knowledge. In this paper, we discuss how we have addressed these demands by adopting a flexible co-design approach that invites the creative blending of mobile technologies and augmented reality with traditional resources, for the purpose of designing innovative mathematical learning activities with high relevance for teachers' practice and the mathematics curriculum.