end.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="app.css">
    <title>Congrats!</title>
</head>
<body>
    <div class="container">
        <div id="end" class="flex-center flex-column">
            <h1 id="finalScore">0</h1>
            <form>
                <input type="text" id="username" name="username" placeholder="username" />
                <button id="saveScoreBtn" type="submit" class="btn" disabled onclick="saveHighScore(event)">
                    Save
                </button>
            </form>
                <a href="game.html" class="btn">Play Again</a>
                <a href="index.html" class="btn">Go Home</a>            
        </div>
    </div>
    <script src="end.js"></script>
</body>
</html>