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
animation:myfirst 5s;10
animation:myfirst 5s; /* Firefox */11
animation:myfirst 5s; /* Safari and Chrome */12
animation:myfirst 5s; /* Opera */13
}14
15
@keyframes myfirst16
{17
0% {background:red;}18
25% {background:yellow;}