index.html

<!DOCTYPE html>
<html>
<style>
    * {
        margin: 0;
        padding: 0;
    }

    body,
    html {
        background-color: black;
        color: white;
    }

    body {
        overflow-x: scroll;
        width: fit-content;
    }

    .char {
        display: inline-block;
        color: white;
        background-color: red;
        padding: 8px;
        width: 20px;
        height: 20px;
        margin: 0px;
        user-select: none;
        text-align: center;
        font-weight: bold;
        border: 2px solid black;
        vertical-align: top;
    }

    .word {
        position: relative;
        display: block;
        height: 42px;
        white-space: nowrap;
    }

    .pattern {
        top: 0px;
        left: 0px;
        width: fit-content;
    }


    .cursor {
        border-top: 2px solid white;
    }

    #playground {
        padding: 16px;
        margin-top: 20px;
    }


    #options {
        position: fixed;
        bottom: 0px;
        padding: 8px;
    }


    .hidden {
        opacity: 0;
    }


    .seen {
        color: white;
    }

</style>

<head>

</head>

<body>

    <div id="playground">
        <div class="word" id="word"></div>
        <div class="word pattern" id="pattern"></div>
    </div>

    <script src="main.js"></script>
</body>

</html>