Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsMotion Traced on the Torus and Klein Bottlehttp://demonstrations.wolfram.com/MotionTracedOnTheTorusAndKleinBottle/]]>http://demonstrations.wolfram.com/MotionTracedOnTheTorusAndKleinBottle/