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                <!DOCTYPE html>
    <canvas id="myCanvas" width="800" height="600" style="border:1px solid #d3d3d3;">
        Your browser does not support the HTML canvas tag.
        var canvas = document.getElementById('myCanvas');
        var ctx = canvas.getContext('2d');

        var x = 50; // initial position of the circle
        var y = 50; // initial position of the circle
        var dx = 2; // change in x
        var dy = 2; // change in y
        var radius = 20; // radius of the circle

        function drawCircle() {
            ctx.arc(x, y, radius, 0, Math.PI * 2, false);
            ctx.fillStyle = 'blue';

        function animate() {
            ctx.clearRect(0, 0, canvas.width, canvas.height); // clear the canvas

            // bounce the circle off the walls
            if (x + dx > canvas.width - radius || x + dx < radius) {
                dx = -dx;

            if (y + dy > canvas.height - radius || y + dy < radius) {
                dy = -dy;

            x += dx;
            y += dy;


        animate(); // start the animation