[4] 回転 (書字方向)
[5] 文字の名前
[1] 回転 (数学) - Wikipedia (2016-10-26 06:15:10 +09:00) https://ja.wikipedia.org/wiki/%E5%9B%9E%E8%BB%A2_(%E6%95%B0%E5%AD%A6)
[2] DeviceOrientation Event Specification (2016-08-19 00:30:43 +09:00) https://w3c.github.io/deviceorientation/spec-source-orientation.html