This article addresses an approach to design-based research informed by cultural historical activity theory and ecological approaches to inquiry in which historicity, prolepsis, remediation, diversity and equity, transformability, resilience, and sustainability are organizing design principles. Social design-based experiments seek to co-design learning ecologies in which learning is made equitable and consequential for youth from nondominant communities. In this article, we focus on the ways the design of <i>El Pueblo Mágico</i>, an after-school STEAM-oriented 5th Dimension program,<i></i> involved saturating the environment with new tools and forms of assistance and privileged intergenerational learning to engage youth and their university amigxs in new technology-mediated practices. In particular, we examine how designing around the leading activity of play opened up opportunities for youth to engage in consequential forms of learning across <i>El Pueblo</i> <i>Mágico</i> and home practices, as well as how digital tools and practices traveled and mediated new learning for young learners.