[4] 回転 (書字方向)
[5] 文字の名前
[1] 回転 (数学) - Wikipedia (10/25/2016, 9:15:10 PM) https://ja.wikipedia.org/wiki/%E5%9B%9E%E8%BB%A2_(%E6%95%B0%E5%AD%A6)
[2] DeviceOrientation Event Specification (8/18/2016, 3:30:43 PM) https://w3c.github.io/deviceorientation/spec-source-orientation.html
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