It is common in some subjects--but not (yet?) in mathematics--to have everything on Powerpoint, prepared in advance of the lecture, and available on-line. Students bring their laptops to lecture (when they come to lecture) and follow along on the web copy. This presupposes you (the lecturer) know in advance what will happen, of course. Unexpected questions are not welcome. And the OP wants to do it at the beginning of the semester!