Physics Script for Roller Ball

PlayerController.cs

using UnityEngine;
using System.Collections;

// Derived from https://unity3d.com/learn/tutorials/projects/roll-ball-tutorial/moving-player?playlist=17141
// Additional comments and renaming of some variables for clarity by Patrick Karjala

public class PlayerController : MonoBehaviour {
  
  // The speed that the object will move at; defaults to 0.
  public float speed;

  // The Rigidbody of the object we’re manipulating; defaults to THIS object.
  private Rigidbody myRigidBody;

  void Start ()
  {
    myRigidBody = GetComponent<Rigidbody>();
  }

  void FixedUpdate ()
  {
    float moveHorizontal = Input.GetAxis ("Horizontal");
    float moveVertical = Input.GetAxis ("Vertical");

    Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

    myRigidBody.AddForce (movement * speed);
  }
}