I recently submitted a short clip for Craig Barton’s podcast on the theme of Slice of Advice: What have I learned this year? In this I suggested two things that had had an impact on me this year: the use of graphing apps on smartphones and diagrams representing functions as mappings between number lines. Graphing apps on smartphones I’ve been using GeoGebra for over ten years now and it has had a huge impact on how I think about mathematics and teaching mathematics. I’ve also been massively impressed with Desmos though I don’t know it inside-out in the way I do with GeoGebra. My use of these graphing tools, and Autograph before it, was always based on using them on a computer and this means I have a preference for the computer software over the phone apps: I find them much more usable on a large screen with a proper keyboard and mouse. This works fine for me but, as I’ve commented on here before, I think the greatest impact of technology in the mathematics classroom is ...