Need some help to achieve reverse spline walk

[manvsrice]

Hello!

I recently downloaded Unity and then last week got the Curvy 2 asset, seems like a great one!

I am trying to use splines to make a 2d game plaformer level with something like a roller-coaster. I was thinking using the tangent for acceleration of speed could be a nice effect. I tried to  change the MotorController.cs example a little bit. The speed increases when going downwards, and decreases when "climbing" a hill nicely, but when it goes below zero it does not go backwards. 

See this youtube video for how it looks: https://www.youtube.com/watch?v=XKrNKKiSY9M

My approach might be wrong? Below is the code I have used:

Code:

   public class MotorController : SplineController
   {
       [Section("Motor")]
       public float MaxSpeed = 30.0f;
       public float acceleration = 3.0f;

       protected override void Update()
       {
           Vector3 tangent = Spline.GetTangentFast(RelativePosition);
           Vector3 orientation = Spline.GetOrientationUpFast(RelativePosition);

           Debug.DrawLine(transform.position, transform.position + tangent * 6.0f, Color.red);
           Debug.DrawLine(transform.position, transform.position + orientation * 6.0f, Color.blue);            

           //Debug.Log("tangent: " + tangent);
           float someAcc = tangent.magnitude * (acceleration * Time.deltaTime) * Mathf.Sign(tangent.y)*-1.0f;
           //Debug.Log("Acc: " + someAcc);

           Speed += someAcc;

           //Speed = Input.GetAxis("Vertical") * MaxSpeed;
           Debug.Log("Speed: " + Speed);
           base.Update();
       }
   }