Unity3D 2D Raycasting

Example.cs

  public Plane gamePlane;

	// Use this for initialization
	void Start () {
	    gamePlane = new Plane(Vector3.zero, Vector3.up, Vector3.right);
	}
	
	// Update is called once per frame
	void Update () {
	  
	  
        if (Input.GetKey(KeyCode.Mouse0))
        {
            //Raycast to see if colliders are hit.
            RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector3.zero);
            if (hit.collider) //Something was hit
            {
                GameObject hitGameObject = hit.collider.gameObject;
            }
            
            //Raycast to get point on 2d plane (to move object there for instance)
             //Raycast into plane that makes up platter that all the sprites are on
            Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            float dist; //Distance of camera to intersection of plane.
            if (solarPlane.Raycast(ray, out dist)) //If 
            {
              Vector3 rayIntersect = ray.GetPoint(dist);
              //Move object that is held, maybe determine delta (save last frame's raycast position).
            }
            
        }
        
        
	}