Thanks. It takes a lot of effort to make live coding that smooth. The initial practice run of a 12-minute screencast was often 30-60 minutes, which would be boring and usually contain less information than the shorter final version. That difference came mostly from sinking effort into it: continuous simplification of examples, explanation, and even wording; and practicing until I (as the speaker) found myself engaged the whole time, with no spots where my attention dipped significantly.