Learner-Centered Design (LCD) is an approach to building software that supports students as they engage in unfamiliar activities and learn about a new area. LCD has been successfully used to support students using desktop computers for a variety of learning activities, and in this paper we discuss new work to extend LCD to the design of educational software for handheld computers. We discuss some of the challenges of designing handheld software and present a case study of ArtemisExpress, a tool that supports learners using handheld computers for online research.