Thinking up new diagrammatic representations for grammatical concepts is excellent fun. I try not to worry about super-scientific accuracy, as the goal is to give the student a visualisation of a concept, but I do like to get them consistent and meaningful. Venn diagrams, mind maps, tree structures, flowcharts and graphs, all wonderful things. I enjoy the element of thinking on my feet, as a grammar rule emerges, finding a clear and accurate representation on the fly. My students aren’t really picking up any science as such with this one, but I think of it as training for when I start slipping in equations.