A steptorial ("step tutorial") is a new interaction strategy for learning complex topics. Conventional tutorials�such as Khan Academy-style videos, or interactive guided tours�require the student to cede control to the tutorial. Many students prefer to dive right in to try to learn how to do something by exploration, but they are quite likely to get lost or confused if the topic is complex. Steptorials are unique because they allow varying the autonomy of the user at every step. A steptorial has a control structure of a reversible programming language stepper. The user may choose, at any time, to be shown how to do a step, be guided through it, to try to attempt the task by themselves, or to return to a previous step. Steptorials introduce a new paradigm of mixed-initiative learning.