Control ball movement by tilting device in Unity3D - unityscript

Question

I'm using the following script to control a ball but it doesn't do exactly what I want.
Our 3D game will be played in landscape mode with the home button (or bottom) of the device in the right hand. Tilting (not turning) the device to the left should make the ball roll left, tilting to the right should make it roll right. Tilting the device down (top of device going down) should make the ball roll faster and tilting the device upward should slow it down.
I don't want the ball to indefinitely accelerate either.
The code below wants the device held straight as opposed to laying flat and it moves the ball by turning the device not by tiling it.
void FixedUpdate()
{
// Player movement in mobile devices
// Building of force vector
Vector3 movement = new Vector3(-Input.acceleration.x, 0.0f, -Input.acceleration.z);
// Adding force to rigidbody
var move = movement * speed * Time.deltaTime;
rigidbdy.AddForce(move);
}

Answer 1

For your tilting problem you likely just need to choose something other than (-Input.acceleration.x, 0.0f, -Input.acceleration.z);, in the example in the documentation they do (-Input.acceleration.y, 0.0f, Input.acceleration.x); to do tilt controls.
For the max speed issue, just add a check for rigidbdy.velocity.magnitude > maxSpeed in your code and cap the value if it is maxed.
public float maxSpeed;
void FixedUpdate()
{
// Player movement in mobile devices
// Building of force vector
Vector3 movement = new Vector3(-Input.acceleration.y, 0.0f, Input.acceleration.x);
// Adding force to rigidbody
var move = movement * speed * Time.deltaTime;
rigidbdy.AddForce(move);
//Limits the max speed
if(rigidbdy.velocity.magnitude > maxSpeed)
{
rigidbdy.velocity = rigidbdy.velocity.normalized * maxSpeed;
}
}
That will cause the velocity to be capped to whatever value you have set for maxSpeed in the inspector.