index.html

<!DOCTYPE HTML>
<html>

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Elm-flatris</title>
    <style>
        html,
        head,
        body {
            padding: 0;
            margin: 0;
        }

        body {
            font-family: sans-serif;
            background: #fff;
        }

        a {
            color: inherit;
            font-weight: 700;
            text-decoration: none;
        }

        a:hover {
            text-decoration: underline;
        }
    </style>
</head>

<body>
    <div id="elm"></div>
    <script src="elm.js"></script>
    <script>
        // Load initial state from localStorage
        var initialState;
        try {
            initialState = JSON.parse(localStorage.getItem('elm-flatris'));
        } catch (e) {

        }

        var app = Elm.Flatris.init({
            node: document.getElementById('elm'),
            flags: initialState
        });
        app.ports.save.subscribe(function (state) {
            // Save game state to localStorage
            localStorage.setItem('elm-flatris', state)
        });

        // Prevent scrolling with arrow and space keys
        window.addEventListener('keydown', function (e) {
            if ([32, 37, 38, 39, 40].indexOf(e.keyCode) > -1) {
                e.preventDefault();
            }
        }, false);

        // Capture focus
        window.focus();
    </script>
</body>

</html>