This paper proposes a novel paradigm: human-centered tabletop computing, which enhances the role of an ordinary table by projecting interactive images onto tabletop objects and the table surface at the same time. The advantage of this approach is that it utilizes tabletop objects as projection screens as well as input tools. As a result, we can change the appearance and role of each tabletop object easily and fulfill two important requirements of tabletop tangible interfaces, identifiability and versatility, which have proven difficult to satisfy simultaneously in previous systems. Our prototype, Tablescape Plus, achieves these functions by using two projectors and a special tabletop screen system that diffuses or transmits images selectively according to the projection orientation. This paper presents the design principle, optical design, and implementation of Table scape Plus. Furthermore, we introduce several interactive applications.