// Update is called once per frame
    void OnGUI ()
    {
        //gui version
        var rect = new Rect (0, 0, Screen.width*0.2f, Screen.height*0.2f);
        if (GUI.Button(rect, "left"))
        {

        }

        //layout version (worse)
        if (GUILayout.Button ("crud", GUILayout.Width(200), GUILayout.ExpandHeight(true)))
        {
        }
        var rect = GUILayoutUtility.GetLastRect();


        //detect mouse in the screen rect of the button
        if (/*Event.current.type.Equals(EventType.MouseUp) && */rect.Contains(Event.current.mousePosition))
        {
            Debug.Log ("mouse");
        }

    }