My Google Summer of Code student, Chas Leichner, started his project this week. His aim is to build a "record, annotate, and replay" extension for IDLE, so that instructors can create program walkthroughs for students. We think this will be better than simple screencasts because they'll be interactive: if a student wants to explore an alternative execution path partway through a replay, or look at some values that the instructor hadn't thought to show, she'll already be in the IDE. (For a rough-and-ready look at what we have in mind, check out Geoff Salmon's web-based prototype.) Chas is blogging at, and his first three posts discuss: We'd welcome comments, particularly on the third post: how instructors add comments or directions to recorded program execution traces is going to be the key determinant of this tool's usability.