Spin on sphere
Eight animated table-tennis balls arranged in a four-by-two grid illustrate common spin types from the server’s perspective. Each sphere rotates continuously, with three mutually perpendicular great circles and a red marker showing the spin axis and direction. The visualization distinguishes topspin, backspin, sidespin, corkscrew, and their combinations based on rotation speeds. Built with D3 v3, it uses an orthographic projection (`d3.geo.orthographic`), graticule, and a `d3.timer` loop to update the paths in SVG. Spin values come from a CSV file.