The entanglement of physical contexts with digital environments is constantly changing our relationship with the surrounding space and creating new hybrid experiences. These transformations pose complex design challenges and yet offer novel opportunities for the understanding and development of human-centered built environments. Drawing from a 5-year design research collaboration between the REAL Lab at Harvard GSD and the University of Bergamo, this book unfolds the experiential facets of our technologically-mediated relationship with space in the fields of architecture, urbanism and art. The book attempts to describe what makes an environment "responsive" in the form of a design manifesto, introducing ten attributes or principles at both methodological and experiential levels. Critically articulated from the perspective of leading experts, scholars and professionals, the ideas explored are unpacked through speculative urban visions and design concepts at different timeframes, contexts and scales ranging from smart artifacts to smart cities.