Code It! fosters mathematics learning environments where pre-algebra students use handheld technologies to explore and learn about functions. The resources developed-server-based and handheld software and paper-based student and teacher texts-were packaged as a 20-session unit on code making and breaking and designed to boost students' understanding of functions and their facility with the multiple representations of tables, graphs and symbols. We field tested the wireless system with two teachers and 120 students during summer school, and conducted studies on the features and function of the technology as a learning and teaching resource. We report on project development and research, focusing on lessons learned about the strengths and difficulties of wireless, handheld technology in the mathematic classroom.