This code only works on 3D Colliders and I want it to work on 2D. What do I need to change?

using UnityEngine; using System.Collections;

public class TouchInput : MonoBehaviour {

 public LayerMask touchInputMask;
 
 private RaycastHit hit;
 
 // Update is called once per frame
 void Update () {
     if(Input.touchCount > 0){
         foreach (Touch touch in Input.touches){
             Ray ray = camera.ScreenPointToRay(touch.position);
             
             if(Physics.Raycast(ray, out hit, touchInputMask)){
             
                 GameObject recepient = hit.transform.gameObject;            
             
                 if(touch.phase == TouchPhase.Began){
                     recepient.SendMessage("OnTouchDown",hit.point,SendMessageOptions.DontRequireReceiver);
                 }
                 if(touch.phase == TouchPhase.Ended){
                     recepient.SendMessage("OnTouchUp",hit.point,SendMessageOptions.DontRequireReceiver);
                 }
                 if(touch.phase == TouchPhase.Stationary || touch.phase == TouchPhase.Moved){
                     recepient.SendMessage("OnTouchStay",hit.point,SendMessageOptions.DontRequireReceiver);
                 }
                 if(touch.phase == TouchPhase.Canceled){
                     recepient.SendMessage("OnTouchExit",hit.point,SendMessageOptions.DontRequireReceiver);
                 }
             }
         }
     }    
 }

}