canvas

1、进度条：（canvas内外半圆进度条）

http://www.17sucai.com/pins/21154.html

https://www.cnblogs.com/eyeear/p/5278092.html

https://developer.mozilla.org/zh-CN/docs/Web/API/Canvas_API/Drawing_DOM_objects_into_a_canvas

http://caibaojian.com/html5-canvas-arc.html