Creating educational software requires a thorough understanding of several key areas: pedagogy, software development and user interface design. This study, which is part of a larger investigation into the impact on learning of educational software for learning equation solving, focuses on user interface design and its relationship to pedagogical principles. User interface features considered include: nature of feedback, screen layout, metaphors, instructions, buttons, and score. This paper is based on trials with real users of educational software at Christchurch Polytechnic Institute of Technology and provides practical information for computing students designing user interfaces.