Point of mouse

http://unityscripts.blogspot.com.ar/2011/10/10-clase-transform.html

http://unityscripts.blogspot.com.ar/p/api-espanol.html

http://docs.unity3d.com/ScriptReference/Physics2D.Raycast.html

http://answers.unity3d.com/questions/547513/how-do-i-detect-when-mouse-passes-over-an-object.html

        Ray ray3 = Camera.main.ScreenPointToRay(Input.mousePosition);
        RaycastHit2D hit3 = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), Vector2.zero);

        if (hit3.collider != null)
        {
            float distance = Mathf.Abs(hit3.point.y - transform.position.y);

            Debug.DrawLine(ray3.origin, hit3.point);

            //se ejecuta cuando el mouse esta sobre una ficha sin la necesidad de hacer click
            Debug.Log(" hit .. " + hit3.collider.name);
        }