Cardiod (Epicycloid, Hypocycloid) via rolling coin
Toggle "animate" to start the outer (planet) coin rolling/revolving round the inner (sun) coin. Toggle "trace" to leave a trail of the pink point, and "curve" to show the path that it travels. The "interval multiplier" extends the trace/curve to cover multiple revolutions. With a little playing around, it should become evident what any other sliders/toggles do.