A ball you can’t see crosses a sheet of lines. Every line is a rigid rod on a pivot. The ball pulls with an inverse-square field, and a rod in that field feels a tidal torque that swings it onto the radial line, the way the Moon keeps one face to the Earth. Or make the ball a wire, and the rods circle it the way compass needles circled Ørsted’s. Nothing here is interpolated: torque, inertia and damping, integrated at 240 Hz. Add a second ball and the fields add, exactly. Move the pointer and the first ball is yours.