Many people rely on what I will call linear presentation tools when they lecture. This includes software such as LibreOffice Impress, Google Presentation, MS PowerPoint, or Keynote. These tools are great for smooth, timed, linear lectures. I also use them from time to time, but mainly if I know exactly what to say. They are also good when I lecture with others, and we need to develop a presentation together. However, linear presentation tools do not work equally well for general teaching, where spontaneity is required.