On Christmas day, my 9-year-old handed me an envelope. In it was his gift for me: his two best hexaflexagons. What’s a hexaflexagon, you might ask? Vi Hart will tell you:
She has more videos and patterns. My son and I wanted to make our own pattern like the fidget spinner one she provides, but the task seemed more pleasurably tackled with mathwork than mousework. So I put together a little utility for assembling such patterns automatically from three source images. And it worked!