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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script type="text/javascript">
    document.addEventListener("DOMContentLoaded", () => {
        let canvas = document.getElementById('canvasId');
        let context = canvas.getContext("2d");

    });

</script>
<style>
    canvas{
        background-color: black;
    }
</style>
</head>
<body>
  <canvas width="800" height="800" id="canvasId"></canvas>
</body>
</html>