Here, the path direction follows the image. Path direction an object are bundled together, with the blue vector. The green/red vector gives the direction and speed of the arm on the path. This is not the only way to arrange the same information. It is up to me whether the wheel, and the path defined on it, are the same information. For example, if the wheel is part of a gear system, the direction of forward rotation may be given elsewhere (say, by a motor). I chose this arrangement to match to the intended behavior of paths on conic sections in GGB: the definition "circle" defines identically a path. Here, the path is [i]oriented[/i]: the circle is defined by A, B, and follows appropriately. The orientation can also be changed. The arm does not jump as B is rotated about A. Pathed objects follows smoothly and the path is continuous under rotation.