https://single9.net/2012/05/leap-motion-%e5%b0%87%e5%bc%95%e7%88%86%e4%ba%ba%e6%a9%9f%e4%ba%92%e5%8b%95%e6%96%b0%e9%9d%a9%e5%91%bd%ef%bc%81/