templates/cats.html

<!DOCTYPE html>
<!--
    Error {{ code }}: {{ message }}
    Description: {{ description }}
-->
<html lang="en">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="robots" content="noindex, nofollow" />
    <title>{{ message }}</title>
    <style>
        html, body {
            margin: 0;
            background-color: #000;
            color: #aaa;
            overflow: hidden;
        }

        .centered {
            height: 100vh;
            align-items: center;
            display: flex;
            justify-content: center
        }

        .centered img {
            max-width: 750px;
            width: 100%;
        }
    </style>
</head>
<body>
    <div class="centered">
        <!-- Pictures provider: <https://http.cat/> -->
        <img src="https://http.cat/{{ code }}.jpg" alt="{{ message }}">
    </div>
</body>
<!--
    Error {{ code }}: {{ message }}
    Description: {{ description }}
-->
</html>