Responsive Fullscreen ( NOT background attachment fixed )

<!DOCTYPE html>
<html lang=en>
<head>
<title></title>
<meta charset=utf-8>
<meta name="viewport" content="width=device-width">
<style>
body {
width:100%;
margin:0;
}
header {
position:absolute;
width:100%;
background-color:/white;
}

h1 {
font-size:40px;
color:white;
text-align:center;
font-family:courier new;
}

#box {
position:absolute;
top:50%;
left:50%;
transform:translate(-50%,-50%);
width:98%;
height:95.5vh;
border:0.5vw solid red;
padding:0.5vw;
}

img {
width:100%;
height:100%;
}

</style>
</head>
<body>

<div id='box'>
<header><h1>Taco with Lime</h1></header>
<img src='https://images.pexels.com/photos/461198/pexels-photo-461198.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=650&w=940' title='Taco'/>
</div>

<script>

</script>
</body>
</html>