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HTML

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

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Vendor Prefixing

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

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Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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HTML 

              
                <div id="content">
  <div id="chat">只要一个三角形</div>
  <div id="chat-b">第二个三角形叠在第一个三角形上面</div>
  <div id="box">底部不规则阴影</div>
</div>
!

CSS 

              
                body{
  font:0.875em "microsoft Yahei";
  color:#333;
  background:#eee;
}
body,ul,h1,h2,h3,p,input{
  margin:0;
  padding:0
}
div{
  box-sizing:border-box;
}
li{
  list-style:none;
}
a{
  text-decoration:none;
}
.clearfix::after{
  content:"";
  display:block;
  clear:both;
}
#content{
  margin:20px auto;
  padding:0 20px;  
}

#chat,#chat-b{
  position:relative;
  width:180px;
  height:180px;
  background:#62C8A5;
  border-radius:5px;
  float:left;
  margin:0 20px 20px 0;
  padding:10px;
}
#chat:before,#chat-b:before,#chat-b:after{
  content:"";
  position:absolute;
  border-bottom:10px solid #62C8A5;
  border-left:10px solid transparent;
  border-right:10px solid transparent;
  top:-10px;
  left:50%;
  margin-left:-10px;
}
#chat-b{
  background:#eee;
  border:2px solid #62C8A5;
}
#chat-b:after{/*第二个三角形叠在第一个三角形上面。*/
  border-left-width:8px;
  border-right-width:8px;
  border-bottom:8px solid #eee;
  margin-left:-8px;
  top:-8px;
}
#box{
  float:left;
  position:relative;
  margin-bottom:30px;
  width:380px;
  height:180px;
  background:#fff;  
  padding:10px;
}
#box:before,#box:after{
  content:"";
  position:absolute;
  width:150px;
  height:10px;
  box-shadow:0 8px 10px rgba(0,0,0,.5);
  bottom:10px;
  z-index:-1;/*必须设置为负数，才能放在自己父元素之下*/
  background:#000;
  
}
#box:before{
  left:20px;
  transform:skewX(-45deg) rotate(-3deg)
}
#box:after{
  right:20px;
  transform:skewX(45deg) rotate(3deg);
}
!

JS
!
999px

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