<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html,
        body {
            width: 100%;
            height: 100%;
            background: #000;
        }
    </style>
</head>

<body>
    <!-- <div class="c1" style="width: 50%;height: 50%;"></div> -->
    <div class="c1" style="width: 310px;height: 320px;"></div>
</body>

</html>