I try very hard not to have any slides. If there is some diagram I simply must show, it goes up when I need to talk about it, and stays there as long as I need

I try very hard not to have any slides. If there is some diagram I simply must show, it goes up when I need to talk about it, and stays there as long as I need to talk about it, and then it comes down again. The lights come back up when I'm done talking about it.