scripts/Rail.cs

using Godot;

public partial class Rail : Area2D
{
    [Export]
    private int bounceDirection = 1;

    public void OnAreaEntered(Area2D area)
    {
        if (area is Ball ball)
        {
            var direction = (ball.Direction + new Vector2(0, bounceDirection)).Normalized();
            ball.Bounce(direction);
        }
    }
}