public void Start()
{
    rb2d = GetComponent<Rigidbody2D>();
    GetComponent<Rigidbody2D>().isKinematic = true;
}

public void OnMouseDown()
{
    screenPoint = Camera.main.WorldToScreenPoint(Four_Object1.transform.position);

    offset = Four_Object1.transform.position - Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z));
}

public void OnMouseDrag()
{

    Vector3 cursorScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);
    cursorPosition = Camera.main.ScreenToWorldPoint(cursorScreenPoint) + offset;
    transform.position = cursorPosition;
}

public void FixedUpdate()
{
    rb2d.MovePosition(cursorPosition);
    Debug.Log("Update!");
}