https://blog.faceutil.com/2017/03/20/msx-%ec%97%98%eb%a6%ac%eb%b2%a0%ec%9d%b4%ed%84%b0-%ec%95%a1%ec%85%98-elevator-action-%e3%82%a8%e3%83%ac%e3%83%99%e3%82%bf%e3%82%a2%e3%82%af%e3%82%b7%e3%83%a7%e3%83%b3-%e3%81%91/