Flick Sprite 2D

I'm trying to flick a sprite which is a ball on touch though it doesn't seem to be responding.



Here is my Script for the ball:

Code (CSharp):

1. public class Puck : MonoBehaviour {
2.  
3.     private const int VECTOR_COUNT = 5;
4.     private int vectorIndex = 0;
5.     private Vector3[] positionChanges;
6.     private Vector3 prevMousePosition;
7.     private float[] prevTimes;
8.     private bool curDown = false;
9.     private bool prevDown = false;
10.  
11.     void Start() {
12.         prevMousePosition = Vector3.zero;
13.         positionChanges = new Vector3[VECTOR_COUNT];
14.         prevTimes = new float[VECTOR_COUNT];
15.         for (int i = 0; i < VECTOR_COUNT; i++) {
16.             positionChanges [i] = Vector3.zero;
17.             prevTimes[i] = 0;
18.         }
19.     }
20.  
21.     void Update () {
22.         if (curDown) {
23.             // if still down just follow the mouse (finger)
24.             Vector3 amountMoved = Camera.main.ScreenToWorldPoint (positionChanges[(vectorIndex - 1 + VECTOR_COUNT) % VECTOR_COUNT]) - Camera.main.ScreenToWorldPoint (new Vector2 (0, 0));
25.             transform.position = transform.position + amountMoved;
26.         } else if(prevDown) {
27.             // just came up so calculate and set velocity
28.             float totalTime = 0;
29.             Vector3 totalDistance = Vector3.zero;
30.             Vector3 velocity;
31.             for(int i = 0; i < VECTOR_COUNT; i++) {
32.                 totalTime += prevTimes[i];
33.                 totalDistance += positionChanges[i];
34.             }
35.             velocity = totalDistance / totalTime;
36.             velocity = Camera.main.ScreenToWorldPoint (velocity) - Camera.main.ScreenToWorldPoint (Vector3.zero);
37.             GetComponent<Rigidbody2D>().velocity = GetComponent<Rigidbody2D>().velocity;
38.         }
39.  
40.         positionChanges [vectorIndex] = Input.mousePosition - prevMousePosition;
41.         prevTimes [vectorIndex] = Time.deltaTime;
42.         vectorIndex = (vectorIndex + 1) % VECTOR_COUNT;
43.  
44.         prevDown = curDown;
45.         prevMousePosition = Input.mousePosition;
46.  
47.         //--------------------------------------------------------------------------------------------------------------
48.          if (!curDown) {
49.              Vector2 temp = GetComponent<Rigidbody2D>().velocity;
50.              if((transform.position.y > Camera.main.orthographicSize && GetComponent<Rigidbody2D>().velocity.y > 0) ||
51.                  (transform.position.y < -Camera.main.orthographicSize && GetComponent<Rigidbody2D>().velocity.y < 0))
52.                  temp.y *= -1;
53.              if((transform.position.x > Camera.main.orthographicSize * Camera.main.aspect && GetComponent<Rigidbody2D>().velocity.x > 0) ||
54.                 (transform.position.x < -Camera.main.orthographicSize * Camera.main.aspect && GetComponent<Rigidbody2D>().velocity.x < 0))
55.                  temp.x *= -1;
56.              GetComponent<Rigidbody2D>().velocity = temp;
57.          }
58.          //-------------------------------------------------------------------------------------------------------------
59.     }
60.  
61.     void OnMouseDown()    {
62.         print ("down");
63.         curDown = true;
64.         GetComponent<Rigidbody2D>().velocity = Vector2.zero;
65.     }
66.  
67.     void OnMouseUp()    {
68.         print ("up");
69.         curDown = false;
70.     }
71. }