子div在父div水平垂直居中

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
        }
        #father {
            width: 500px;
            height: 500px;
            background: lightcoral;
            margin: 100px auto;

            display: flex;
            justify-content: center;
            align-items: center;
        }
        #son{
            width: 200px;
            height: 200px;
            background: lightskyblue;
        }
    </style>
</head>
<body>
<div id="wrap">
    <div id="box"></div>
</div>
</body>
</html>