javascript - how do i make the ball collide and bounce off my paddle -


im uni student having make kind of breakout clone in html. have ball bounce off rectangles ive drawn , paddle. problem im still new html , cant seem find solution works code have work off of. taking time read.

var canvas = document.getelementbyid("pong");  var ctx = canvas.getcontext("2d");    var ball = {    x: canvas.width / 2,   //pixels    y: canvas.height / 2,  //pixels    xspeed: 50,           //pixels per second (you can cahnge this)    yspeed: 40,           //pixels per second (you can change this)    radius: 10             //pixels  }    var paddle = {    x: 100,   			//pixels    y: canvas.height / 2,  //pixels    xspeed: 10,           //pixels per second (you can increase this)    yspeed: 10,           //pixels per second (you can increase this)    halfwidth: 10, 		//pixels    halfheight: 40		//pixels  }    // todo: add data top, bottom, left , right rectangles      var topwall = {      x:0,      y:0,      width:800,      height:10,      area:8000    }      var bottomwall = {      x:0,      y:400,      width:800,      height:10,      area:8000    }      var rightwall = {      x:800,      y:0,      width:10,      height:400,      area:4000    }      var leftwall = {      x:0,      y:0,      width:10,      height:400,      area:4000    }    // function draw  function render() {    //clear canvas    ctx.clearrect(0, 0, canvas.width, canvas.height);      // draw ball    ctx.fillstyle = "white";    ctx.beginpath();    ctx.arc(ball.x, ball.y, ball.radius, 0, math.pi * 2);    ctx.fill();      // draw paddle    ctx.beginpath();    ctx.moveto(paddle.x - paddle.halfwidth, paddle.y - paddle.halfheight);    ctx.lineto(paddle.x - paddle.halfwidth, paddle.y + paddle.halfheight);    ctx.lineto(paddle.x + paddle.halfwidth, paddle.y + paddle.halfheight);    ctx.lineto(paddle.x + paddle.halfwidth, paddle.y - paddle.halfheight);    ctx.fill();      // todo: draw top, bottom, left , right rectangles      // drawing right wall    ctx.strokestyle = "white";    ctx.fillstyle = "white";    ctx.beginpath();    ctx.moveto(rightwall.x, rightwall.y);    ctx.lineto(rightwall.x - rightwall.width, rightwall.y);    ctx.lineto(rightwall.x - rightwall.width, rightwall.y + rightwall.height);    ctx.lineto(rightwall.x, rightwall.y + rightwall.height);    ctx.closepath();    ctx.stroke();    ctx.fill();      //top wall    ctx.strokestyle = "white";    ctx.fillstyle = "white";    ctx.beginpath();    ctx.moveto(topwall.x, topwall.y);    ctx.lineto(topwall.x + topwall.width, topwall.y);    ctx.lineto(topwall.x + topwall.width, topwall.y + topwall.height);    ctx.lineto(topwall.x, topwall.y + topwall.height);    ctx.closepath();    ctx.stroke();    ctx.fill();      //bottom wall    ctx.strokestyle = "white";    ctx.fillstyle = "white";    ctx.beginpath();    ctx.moveto(bottomwall.x, bottomwall.y);    ctx.lineto(bottomwall.x + bottomwall.width, bottomwall.y);    ctx.lineto(bottomwall.x + bottomwall.width, bottomwall.y - bottomwall.height);    ctx.lineto(bottomwall.x, bottomwall.y - bottomwall.height);    ctx.closepath();    ctx.stroke();    ctx.fill();     //left wall    ctx.strokestyle = "white";    ctx.fillstyle = "white";    ctx.beginpath();    ctx.moveto(leftwall.x, leftwall.y);    ctx.lineto(leftwall.x + leftwall.width, leftwall.y);    ctx.lineto(leftwall.x + leftwall.width, leftwall.y + leftwall.height);    ctx.lineto(leftwall.x, leftwall.y + leftwall.height);    ctx.closepath();    ctx.stroke();    ctx.fill();    }    // function updates game physics  function update(elapsed) {    //update ball position according elapsed time    ball.y += ball.yspeed * elapsed;    ball.x += ball.xspeed * elapsed;      // todo: bounce ball of top, bottom , right rectangles    // todo: end game (stop ball moving) if ball hits left rectangle    // todo: bounce ball off paddle  }    // handle keyboard input   function keydown_handler(e) {    // todo: modify code paddle goes , down not outside area of play.          switch (event.keycode){            case 38: //up key (move paddle up)            if (paddle.y - 30 > 49) {              paddle.y -= 30;            }            break;            case 40: // down key (move paddle down)            if (paddle.y + 30 < 360) {              paddle.y += 30;            }            break;          }        }    window.addeventlistener("keydown", keydown_handler);    var previous;  function run(timestamp) {    if (!previous) previous = timestamp;          //start no elapsed time    var elapsed = (timestamp - previous) / 1000;  //work out elapsed time    update(elapsed);                              //update game elapsed time    render();                                     //render scene    previous = timestamp;                         //set (globally defined) previous timestamp ready next time    window.requestanimationframe(run);            //ask browser call function again, when it's ready  }    //trigger game loop  window.requestanimationframe(run);
body {    font-family: "century gothic";  }    main, header {    max-width: 60%;    margin: 0 auto;  }    header h1 {    font-size: 6em;    margin: 0;  }    canvas#pong {    background: #45484d; /* old browsers */    background: radial-gradient(ellipse @ center, #45484d 0%,#000000 100%); /* w3c */    border-radius: 10px;    border: 4px solid #d5282d;    width: 100%;  }
<!doctype html>  <html>    <head>      <title>pong - resit cw</title>      <link rel="stylesheet" href="pong.css" media="screen" title="no title" charset="utf-8">    </head>    <body style="overflow:hidden;">      <header>        <h1>pong</h1>      </header>      <main>        <canvas id="pong" width="800" height="400"></canvas>        <p>          task complete following:          <ul>            <li>add data 4 rectangles around edge of play area.</li>            <li>draw these 4 rectangles.</li>            <li>alter game physics ball bounces off these rectangles , paddle.</li>            <li>add keyboard controls paddle moves , down when , down arrow keys pressed.</li>            <li>end game (stop ball moving) when ball hits left rectangle.</li>          </ul>        </p>        <p>          of these alterations need made in pong.js file.          code marked //todo: give hints functionality needs added.        </p>      </main>      <script charset="utf-8" src="pong.js"></script>    </body>  </html>


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