一共收集整理了图形20个，比较实用，同时也为了熟悉CSS的代码

1.正方形

square {
width: 100px; height: 100px; background: red;}

2.长方形

rectangle { width: 200px; height: 100px; background: red;}
3.左上三角

triangle-topleft { width: 0; height: 0; border-top: 100px solid red; border-right: 100px solid transparent; }
4.右上三角

triangle-topright { width: 0; height: 0; border-top: 100px solid red; border-left: 100px solid transparent;}
5.左下三角

triangle-bottomleft { width: 0; height: 0; border-bottom: 100px solid red; border-right: 100px solid transparent; }
6.右下三角

triangle-bottomright { width: 0; height: 0; border-bottom: 100px solid red; border-left: 100px solid transparent; }
7.平行四边形

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

trapezoid { border-bottom: 100px solid red; border-left: 50px solid transparent; border-right: 50px solid transparent; height: 0; width: 100px; }
9.六角星

star-six { width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-bottom: 100px solid red; position: relative; } #star-six:after { width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-top: 100px solid red; position: absolute; content: ""; top: 30px; left: -50px; }
10.五角星

star-five { margin: 50px 0; position: relative; display: block; color: red; width: 0px; height: 0px; border-right: 100px solid transparent; border-bottom: 70px solid red; border-left: 100px solid transparent; -moz-transform: rotate(35deg); -webkit-transform: rotate(35deg); -ms-transform: rotate(35deg); -o-transform: rotate(35deg); } #star-five:before { border-bottom: 80px solid red; border-left: 30px solid transparent; border-right: 30px solid transparent; position: absolute; height: 0; width: 0; top: -45px; left: -65px; display: block; content: ""; -webkit-transform: rotate(-35deg); -moz-transform: rotate(-35deg); -ms-transform: rotate(-35deg); -o-transform: rotate(-35deg); } #star-five:after { position: absolute; display: block; color: red; top: 3px; left: -105px; width: 0px; height: 0px; border-right: 100px solid transparent; border-bottom: 70px solid red; border-left: 100px solid transparent; -webkit-transform: rotate(-70deg); -moz-transform: rotate(-70deg); -ms-transform: rotate(-70deg); -o-transform: rotate(-70deg); content: ""; }
11.五边形

pentagon { position: relative; width: 54px; border-width: 50px 18px 0; border-style: solid; border-color: red transparent; } #pentagon:before { content: ""; position: absolute; height: 0; width: 0; top: -85px; left: -18px; border-width: 0 45px 35px; border-style: solid; border-color: transparent transparent red; }
12.六边形

hexagon { width: 100px; height: 55px; background: red; position: relative; } #hexagon:before { content: ""; position: absolute; top: -25px; left: 0; width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-bottom: 25px solid red; } #hexagon:after { content: ""; position: absolute; bottom: -25px; left: 0; width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-top: 25px solid red; }
13.桃心

heart { position: relative; width: 100px; height: 90px; } #heart:before, #heart:after { position: absolute; content: ""; left: 50px; top: 0; width: 50px; height: 80px; background: red; -moz-border-radius: 50px 50px 0 0; border-radius: 50px 50px 0 0; -webkit-transform: rotate(-45deg); -moz-transform: rotate(-45deg); -ms-transform: rotate(-45deg); -o-transform: rotate(-45deg); transform: rotate(-45deg); -webkit-transform-origin: 0 100%; -moz-transform-origin: 0 100%; -ms-transform-origin: 0 100%; -o-transform-origin: 0 100%; transform-origin: 0 100%; } #heart:after { left: 0; -webkit-transform: rotate(45deg); -moz-transform: rotate(45deg); -ms-transform: rotate(45deg); -o-transform: rotate(45deg); transform: rotate(45deg); -webkit-transform-origin: 100% 100%; -moz-transform-origin: 100% 100%; -ms-transform-origin: 100% 100%; -o-transform-origin: 100% 100%; transform-origin :100% 100%; }
14。无限大符号

infinity { position: relative; width: 212px; height: 100px; }
infinity:before, #infinity:after { content: ""; position: absolute; top: 0; left: 0; width: 60px; height: 60px; border: 20px solid red; -moz-border-radius: 50px 50px 0 50px; border-radius: 50px 50px 0 50px; -webkit-transform: rotate(-45deg); -moz-transform: rotate(-45deg); -ms-transform: rotate(-45deg); -o-transform: rotate(-45deg); transform: rotate(-45deg); }
infinity:after { left: auto; right: 0; -moz-border-radius: 50px 50px 50px 0; border-radius: 50px 50px 50px 0; -webkit-transform: rotate(45deg); -moz-transform: rotate(45deg); -ms-transform: rotate(45deg); -o-transform: rotate(45deg); transform: rotate(45deg); }
15.蛋

egg { display:block; width: 126px; height: 180px; background-color: red; -webkit-border-radius: 63px 63px 63px 63px / 108px 108px 72px 72px; border-radius: 50% 50% 50% 50% / 60% 60% 40% 40%; }
16.提示对话框

talkbubble { width: 120px; height: 80px; background: red; position: relative; -moz-border-radius: 10px; -webkit-border-radius: 10px; border-radius: 10px; } #talkbubble:before { content:""; position: absolute; right: 100%; top: 26px; width: 0; height: 0; border-top: 13px solid transparent; border-right: 26px solid red; border-bottom: 13px solid transparent; }
17.十二角星

burst-8 { background: red; width: 80px; height: 80px; position: relative; text-align: center; -webkit-transform: rotate(20deg); -moz-transform: rotate(20deg); -ms-transform: rotate(20deg); -o-transform: rotate(20eg); transform: rotate(20deg); } #burst-8:before { content: ""; position: absolute; top: 0; left: 0; height: 80px; width: 80px; background: red; -webkit-transform: rotate(135deg); -moz-transform: rotate(135deg); -ms-transform: rotate(135deg); -o-transform: rotate(135deg); transform: rotate(135deg); }
18.八角星

burst-8 { background: red; width: 80px; height: 80px; position: relative; text-align: center; -webkit-transform: rotate(20deg); -moz-transform: rotate(20deg); -ms-transform: rotate(20deg); -o-transform: rotate(20eg); transform: rotate(20deg); } #burst-8:before { content: ""; position: absolute; top: 0; left: 0; height: 80px; width: 80px; background: red; -webkit-transform: rotate(135deg); -moz-transform: rotate(135deg); -ms-transform: rotate(135deg); -o-transform: rotate(135deg); transform: rotate(135deg); }
19.钻石

cut-diamond { border-style: solid; border-color: transparent transparent red transparent; border-width: 0 25px 25px 25px; height: 0; width: 50px; position: relative; margin: 20px 0 50px 0; } #cut-diamond:after { content: ""; position: absolute; top: 25px; left: -25px; width: 0; height: 0; border-style: solid; border-color: red transparent transparent transparent; border-width: 70px 50px 0 50px; }
20.八卦

yin-yang { width: 96px; height: 48px; background: #eee; border-color: red; border-style: solid; border-width: 2px 2px 50px 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; }