<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
body,
html {
height: 100%;
margin: 0;
padding: 0;
/* display: flex;
justify-content: center;
align-items: center; */
}
.father {
width: 100%;
height: 100%;
position: relative;
border: 1px solid red;
}
.son {
background: red;
width: 200px;
height: 200px;
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%)
}
</style>
</head>
<body>
<div class="father">
<div class="son"></div>
</div>
</body>
</html>
效果：
