index.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Realtime Drawing</title>
    <script src="script.js" type="module"></script>
</head>

<body>
    <div class="container">
        <div>
            <canvas id="drawing-canvas" width="1200" height="600"></canvas>
            <div class="buttons">
                <button id="blue-btn">Blue</button>
                <button id="red-btn">Red</button>
                <button id="green-btn">Green</button>
                <button id="yellow-btn">Yellow</button>
            </div>
        </div>
    </div>
</body>
<style>
    html,
    body {
        height: 100%;
        padding: 0;
        background-color: black;
    }

    .buttons {
        display: flex;
        justify-content: center;
    }

    button {
        margin-right: 15px;
    }

    .container {
        display: flex;
        justify-content: center;
        align-items: center;
        height: 100%;
        padding: 0;
    }

    #drawing-canvas {
        background-color: white;
        border: 2px solid black;
    }
</style>

</html>