CSS还是比较强大的，可以实现中国古典的“阴阳八卦图”等形状。

正方形

#rectangle { width: 200px; height: 100px; backgrount-color: red; }  #circle { width: 100px; height: 100px; -webkit-border-radius: 100px; -moz-border-radius: 100px; border-radius: 100px; background-color: red; }

椭圆

#triangle-up { width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-bottom: 100px solid red; }

直角三角形

直角边left-top

#triangle-leftbottom { width: 0; height: 0; border-left: 100px solid red; border-top: 100px solid transparent; }

直角边right-top

#triangle-righttop { width: 0; height: 0; border-right: 100px solid red; border-top: 100px solid transparent; }

梯形

#parallelogram { width: 150px; height: 100px; -webkit-transform: skew(20deg); -moz-transform: skew(20deg); transform: skew(20deg); background: red; }

鸡蛋

#yin-yang { width: 96px; height: 48px; background: #eee; border-color: red; border-style: solid; border-width: 2px 2px 55px 2px; border-radius: 100%; position: relative; }  #yin-yang:before { content: ""; position: absolute; top: 50%; left: 0; background: #eee; border: 18px solid red; border-radius: 100%; width: 12px; height: 12px; }  #yin-yang:after { content: ""; position: absolute; top: 50%; left: 50%; background: red; border: 18px solid #eee; border-radius:100%; width: 12px; height: 12px; } 八卦图展示不出来，蛋疼，请下载HTML文件 或者 去  查看

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