Out of the box, characters can move forward and backwards and they can move upstairs and downstairs. They can move backwards downstairs, but not backwards upstairs. Small feature, but if there is a small rock behind the character, it would get stuck as it retreats while fighting the evil horde.
I modified vThirdPersonMotor.cs so that the ray to look at the stairs looks backwards when speed is less than zero, and pushes the character upward (instead of down).
Please review the code below for improvements. Hope this helps others.