text and background

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Responsive Text Banner</title>
    <style>
        .banner {
            background-color: black;
            color: white;
            font-weight: 700;
            padding: 10px;
            font-size: 1.2em;
            width: 100%;
            box-sizing: border-box;
        }
        @media (max-width: 600px) {
            .banner {
                font-size: 1em;
                padding: 8px;
            }
        }
    </style>
</head>
<body>
    <div class="banner">
        Backed by Science Guaranteed! Only contains high-quality and clinically validated ingredients.
    </div>
</body>
</html>