<!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>