*{margin: 0;padding: 0;}
@media screen and (min-width: 320px){
html{
font-size: 50px;
}
}
@media screen and (min-width: 640px){
html{
font-size: 100px;
}
}
#top{
height: 1rem;
font-size: .5rem;
line-height: 1rem;
background-color: darkmagenta;
color: #ffffff;
}
</style>
</head>
<body>
<div id="top">
购物车
</div>
</body>
