This paper discusses the results of a study of students' use of EPIC, a system for teaching the generation of logic proofs. Besides providing information about the goals, plans and beliefs of the student, the system was also found to behave as a supportive learning environment. The ' features of the system that had these beneficial effects are described and discussed, as are various difficulties which the students displayed when attempting to learn using the system that have general implications for the development of better learning environments. The observations indicate the great influence of the interface in any learning environment. This can make traditional experimental assessment of the effect of tutoring features problematic. A methodology of small in-depth studies coupled with rapid prototyping is proposed as a desirable mechanism for tutoring system development.