How CSS draws a fan of any angle

Fan-making principle, the bottom of a solid color prototype, inside 2 of the same color of the semi-circle, can be white, the internal semicircle at a certain angle, you can produce a fan effect

 The following is a more complex doughnut shape that combines css+html5+javascript 
 

<%@ page language= "java" import= "java.util.*" pageencoding= "utf-8"%><%string path = Request.getcontextpath () ; String basepath = request.getscheme () + "://" +request.getservername () + ":" +request.getserverport () +path+ "/";%> <! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" >