代码编辑器：
x
1
2
<meta charset="utf-8"><link href="/static/next/css/tryit.css?v=2017082407" rel="stylesheet"/>3
<style>4
div5
{6
width:100px;7
height:100px;8
background:red;9
transition:width 2s;10
transition:width 2s; /* Safari */11
}12
13
div:hover14
{15
width:300px;16
}17
</style>18