I was wondering if anyone had a more precise explanation that was based on how the game was supposed to work, rather than just experimentation. Also, are there just 3 modes (straight, left-curve and right-curve) or can the degree of curvature be controlled.
IMO a better way of controlling the curvature would have been to directly manipulate the node-orientation. To do this, a smaller circle that resembles the end-node circle should be at a fixed distance from the end-node marker, and this smaller circle can be rotated round the big circle using the mouse to drag it round.