<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>九宫格</title>
</head>
<style>
.wrapper {
width: 300px;
height: 300px;
display: grid;
grid-template-columns: 1fr 1fr 1fr;
grid-template-rows: 1fr 1fr 1fr;
}
.wrapper div {
border: 4px solid gray;
box-sizing: border-box;
display: flex;
justify-content: center;
align-items: center;
margin-left: -4px;
margin-top: -4px;
/* 负边距解决边框重叠问题 */
}
.wrapper div:hover{
border: 4px solid red;
z-index: 2;
/* 解决边框显示问题 */
}
</style>
<body>
<section class="wrapper">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
<div>5</div>
<div>6</div>
<div>7</div>
<div>8</div>
<div>9</div>
</section>
</body>
</html>体现：样式重置，标签语义化，边框问题，盒模型
