All of the below use only a single HTML element. Any kind of CSS goes, as long as it's supported in at least one browser.
（下面的所有内容只使用一个HTML元素。任何一种CSS都可以，只要它在至少一个浏览器中支持。）
Square （正方形）
#square { width: 100px; height: 100px; background: red; }
Rectangle （长方形）
#rectangle { width: 200px; height: 100px; background: red; }
Circle （圆形）
#circle { width: 100px; height: 100px;
background: red;
-moz-border-radius: 50px;
-webkit-border-radius: 50px;
border-radius: 50px;
} /* Cleaner, but slightly less support: use "50%" as value */
半圆形（Semicircle）
扇形（Fan-Shaped）
https://www.w3cplus.com/css/create-shapes-with-css
Oval （椭圆形；卵形）
#oval {
width: 200px; height: 100px;
background: red;
-moz-border-radius: 100px / 50px;
-webkit-border-radius: 100px / 50px;
border-radius: 100px / 50px; } /* Cleaner, but slightly less support: use "50%" as value */
Triangle Up
#triangle-up { width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-bottom: 100px solid red; }
Triangle Down
#triangle-down { width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-top: 100px solid red; }
Triangle Left
#triangle-left { width: 0; height: 0; border-top: 50px solid transparent; border-right: 100px solid red; border-bottom: 50px solid transparent; }
Triangle Right
#triangle-right { width: 0; height: 0; border-top: 50px solid transparent; border-left: 100px solid red; border-bottom: 50px solid transparent; }
Triangle Top Left
#triangle-topleft { width: 0; height: 0; border-top: 100px solid red; border-right: 100px solid transparent; }
Triangle Top Right
#triangle-topright { width: 0; height: 0; border-top: 100px solid red; border-left: 100px solid transparent; }
Triangle Bottom Left
#triangle-bottomleft { width: 0; height: 0; border-bottom: 100px solid red; border-right: 100px solid transparent; }
Triangle Bottom Right
#triangle-bottomright { width: 0; height: 0; border-bottom: 100px solid red; border-left: 100px solid transparent; }
Curved Tail Arrow （弯曲的尾巴箭头） via Ando Razafimandimby
#curvedarrow { position: relative; width: 0; height: 0; border-top: 9px solid transparent; border-right: 9px solid red; -webkit-transform: rotate(10deg); -moz-transform: rotate(10deg); -ms-transform: rotate(10deg); -o-transform: rotate(10deg); }
#curvedarrow:after {
content: "";
position: absolute;
border: 0 solid transparent;
border-top: 3px solid red;
border-radius: 20px 0 0 0;
top: -12px;
left: -9px;
width: 12px;
height: 12px;
-webkit-transform: rotate(45deg);
-moz-transform: rotate(45deg);
-ms-transform: rotate(45deg);
-o-transform: rotate(45deg);
}
Trapezoid（梯形）
#trapezoid { border-bottom: 100px solid red; border-left: 50px solid transparent; border-right: 50px solid transparent; height: 0; width: 100px; }
Parallelogram（平行四边形）
#parallelogram { width: 150px; height: 100px; -webkit-transform: skew(20deg); -moz-transform: skew(20deg); -o-transform: skew(20deg); background: red; }
Star (6-points) （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; }
Star (5-points) （五角星） via Kit MacAllister
#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: '';
}
Pentagon （五角形）
#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; }
Hexagon （六角形）
#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; }
Octagon （八边形）
#octagon { width: 100px; height: 100px; background: red; position: relative; }
#octagon:before { content: ""; position: absolute; top: 0; left: 0; border-bottom: 29px solid red; border-left: 29px solid #eee; border-right: 29px solid #eee; width: 42px; height: 0; }
#octagon:after { content: ""; position: absolute; bottom: 0; left: 0; border-top: 29px solid red; border-left: 29px solid #eee; border-right: 29px solid #eee; width: 42px; height: 0; }
Heart （心形） via Nicolas Gallagher
#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%;
}
#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);
}
Diamond Square （钻石形） via Joseph Silber
#diamond {
width: 0;
height: 0;
border: 50px solid transparent;
border-bottom-color: red;
position: relative;
top: -50px;
}
#diamond:after {
content: '';
position: absolute;
left: -50px;
top: 50px;
width: 0;
height: 0;
border: 50px solid transparent;
border-top-color: red;
}
content: '';
position: absolute;
left: -50px;
top: 50px;
width: 0;
height: 0;
border: 50px solid transparent;
border-top-color: red;
}
Diamond Shield （钻石 盾牌） via Joseph Silber
#diamond-shield {
width: 0;
height: 0;
border: 50px solid transparent;
border-bottom: 20px solid red;
position: relative;
top: -50px;
}
width: 0;
height: 0;
border: 50px solid transparent;
border-bottom: 20px solid red;
position: relative;
top: -50px;
}
#diamond-shield:after {
content: '';
position: absolute;
left: -50px; top: 20px;
width: 0;
height: 0;
border: 50px solid transparent;
border-top: 70px solid red;
}
content: '';
position: absolute;
left: -50px; top: 20px;
width: 0;
height: 0;
border: 50px solid transparent;
border-top: 70px solid red;
}
Diamond Narrow via Joseph Silber
#diamond-narrow {
width: 0;
height: 0;
border: 50px solid transparent;
border-bottom: 70px solid red;
position: relative;
top: -50px;
}
width: 0;
height: 0;
border: 50px solid transparent;
border-bottom: 70px solid red;
position: relative;
top: -50px;
}
#diamond-narrow:after {
content: '';
position: absolute;
left: -50px; top: 70px;
width: 0;
height: 0;
border: 50px solid transparent;
border-top: 70px solid red;
}
content: '';
position: absolute;
left: -50px; top: 70px;
width: 0;
height: 0;
border: 50px solid transparent;
border-top: 70px solid red;
}
Cut Diamondvia Alexander Futekov
#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; }
Egg （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%; }
Pac-Man （吃豆人）
#pacman { width: 0px; height: 0px; border-right: 60px solid transparent; border-top: 60px solid red; border-left: 60px solid red; border-bottom: 60px solid red; border-top-left-radius: 60px; border-top-right-radius: 60px; border-bottom-left-radius: 60px; border-bottom-right-radius: 60px; }
https://www.w3cplus.com/css/css-simple-shapes-cheat-sheet
Talk Bubble （对话泡泡）
#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; }
12 Point Burst （12点破裂） via Alan Johnson
#burst-12 { background: red; width: 80px; height: 80px; position: relative; text-align: center; }
#burst-12:before, #burst-12:after { content: ""; position: absolute; top: 0; left: 0; height: 80px; width: 80px; background: red; }
#burst-12:before { -webkit-transform: rotate(30deg); -moz-transform: rotate(30deg); -ms-transform: rotate(30deg); -o-transform: rotate(30deg); }
#burst-12:after { -webkit-transform: rotate(60deg); -moz-transform: rotate(60deg); -ms-transform: rotate(60deg); -o-transform: rotate(60deg); }
8 Point Burst （8点破裂） via Alan Johnson
#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); }
#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); }
Yin Yangvia Alexander Futekov （阴阳图）
#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; }
Badge Ribbon （徽章丝带） via Catalin Rosu
#badge-ribbon { position: relative; background: red; height: 100px; width: 100px; -moz-border-radius: 50px; -webkit-border-radius: 50px; border-radius: 50px; }
#badge-ribbon:before,
#badge-ribbon:after { content: ''; position: absolute; border-bottom: 70px solid red; border-left: 40px solid transparent; border-right: 40px solid transparent; top: 70px; left: -10px; -webkit-transform: rotate(-140deg); -moz-transform: rotate(-140deg); -ms-transform: rotate(-140deg); -o-transform: rotate(-140deg); }
#badge-ribbon:after { left: auto; right: -10px; -webkit-transform: rotate(140deg); -moz-transform: rotate(140deg); -ms-transform: rotate(140deg); -o-transform: rotate(140deg); }
Space Invader （小蜜蜂 太空侵旅者） via Vlad Zinculescu
#space-invader{ box-shadow: 0 0 0 1em red, 0 1em 0 1em red, -2.5em 1.5em 0 .5em red, 2.5em 1.5em 0 .5em red, -3em -3em 0 0 red, 3em -3em 0 0 red, -2em -2em 0 0 red, 2em -2em 0 0 red, -3em -1em 0 0 red, -2em -1em 0 0 red, 2em -1em 0 0 red, 3em -1em 0 0 red, -4em 0 0 0 red, -3em 0 0 0 red, 3em 0 0 0 red, 4em 0 0 0 red, -5em 1em 0 0 red, -4em 1em 0 0 red, 4em 1em 0 0 red, 5em 1em 0 0 red, -5em 2em 0 0 red, 5em 2em 0 0 red, -5em 3em 0 0 red, -3em 3em 0 0 red, 3em 3em 0 0 red, 5em 3em 0 0 red, -2em 4em 0 0 red, -1em 4em 0 0 red, 1em 4em 0 0 red, 2em 4em 0 0 red; background: red; width: 1em; height: 1em; overflow: hidden; margin: 50px 0 70px 65px; }
TV Screen （电视屏幕）
#tv { position: relative; width: 200px; height: 150px; margin: 20px 0; background: red; border-radius: 50% / 10%; color: white; text-align: center; text-indent: .1em; }
#tv:before { content: ''; position: absolute; top: 10%; bottom: 10%; right: -5%; left: -5%; background: inherit; border-radius: 5% / 50%; }
Chevron （V形肩章） via Anthony Ticknor
#chevron { position: relative; text-align: center; padding: 12px; margin-bottom: 6px; height: 60px; width: 200px; }
#chevron:before { content: ''; position: absolute; top: 0; left: 0; height: 100%; width: 51%; background: red; -webkit-transform: skew(0deg, 6deg); -moz-transform: skew(0deg, 6deg); -ms-transform: skew(0deg, 6deg); -o-transform: skew(0deg, 6deg); transform: skew(0deg, 6deg); }
#chevron:after { content: ''; position: absolute; top: 0; right: 0; height: 100%; width: 50%; background: red; -webkit-transform: skew(0deg, -6deg); -moz-transform: skew(0deg, -6deg); -ms-transform: skew(0deg, -6deg); -o-transform: skew(0deg, -6deg); transform: skew(0deg, -6deg); }
Magnifying Glass （放大镜）
#magnifying-glass { font-size: 10em; /* This controls the size. */ display: inline-block; width: 0.4em; height: 0.4em; border: 0.1em solid red; position: relative; border-radius: 0.35em; }
#magnifying-glass::before { content: ""; display: inline-block; position: absolute; right: -0.25em; bottom: -0.1em; border-width: 0; background: red; width: 0.35em; height: 0.08em; -webkit-transform: rotate(45deg); -moz-transform: rotate(45deg); -ms-transform: rotate(45deg); -o-transform: rotate(45deg); }
Facebook Icon （Facebook的图标） via Nathan Swartz
#facebook-icon { background: red; text-indent: -999em; width: 100px; height: 110px; border-radius: 5px; position: relative; overflow: hidden; border: 15px solid red; border-bottom: 0; }
#facebook-icon::before { content: "/20"; position: absolute; background: red; width: 40px; height: 90px; bottom: -30px; right: -37px; border: 20px solid #eee; border-radius: 25px; }
#facebook-icon::after { content: "/20"; position: absolute; width: 55px; top: 50px; height: 20px; background: #eee; right: 5px; }
Moon （月亮） via Omid Rasouli
#moon { width: 80px; height: 80px; border-radius: 50%; box-shadow: 15px 15px 0 0 red; }
Flag （标志 旗子 ） via Zoe Rooney
#flag { width: 110px; height: 56px; padding-top: 15px; position: relative; background: red; color: white; font-size: 11px; letter-spacing: 0.2em; text-align: center; text-transform: uppercase; }
#flag:after { content: ""; position: absolute; left: 0; bottom: 0; width: 0; height: 0; border-bottom: 13px solid #eee; border-left: 55px solid transparent; border-right: 55px solid transparent; }
Cone （圆锥形） via Omid Rasouli
#cone { width: 0; height: 0; border-left: 70px solid transparent; border-right: 70px solid transparent; border-top: 100px solid red; -moz-border-radius: 50%; -webkit-border-radius: 50%; border-radius: 50%; }
Cross （十字架） via Kaya Basharan
#cross { background: red; height: 100px; position: relative; width: 20px; } #cross:after { background: red; content: ""; height: 20px; left: -40px; position: absolute; top: 40px; width: 100px; }
Base （垒） via Josh Rodgers
#base { background: red; display: inline-block; height: 55px; margin-left: 20px; margin-top: 55px; position: relative; width: 100px; }
#base:before { border-bottom: 35px solid red; border-left: 50px solid transparent; border-right: 50px solid transparent; content: ""; height: 0; left: 0; position: absolute; top: -35px; width: 0; }
Pointer （指针） via Amsakanna Freethinker
#pointer { width: 200px; height: 40px; position: relative; background: red; } #pointer:after { content: ""; position: absolute; left: 0; bottom: 0; width: 0; height: 0; border-left: 20px solid white; border-top: 20px solid transparent; border-bottom: 20px solid transparent; } #pointer:before { content: ""; position: absolute; right: -20px; bottom: 0; width: 0; height: 0; border-left: 20px solid red; border-top: 20px solid transparent; border-bottom: 20px solid transparent; }
表图（chartColorful）
link：https://css-tricks.com/examples/ShapesOfCSS/