HTML5 Canvas Star Spinner

Instructions: Spin the star with your mouse.

Code Editor

<!DOCTYPE HTML>
<html>
  <head>
    <style>
      body {
        margin: 0px;
        padding: 0px;
      }
    </style>
  </head>
  <body>
    <div id="container"></div>
    <script src="http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.5.2.min.js"></script>
    <script>
      function animate(animatedLayer, star, frame) {
        // 20% slow down per second
        var angularFriction = 0.2;
        var angularVelocityChange = star.angularVelocity * frame.timeDiff * (1 - angularFriction) / 1000;
        star.angularVelocity -= angularVelocityChange;

if(star.controlled) {
          star.angularVelocity = (star.getRotation() - star.lastRotation) * 1000 / frame.timeDiff;
        }
        else {
          star.rotate(frame.timeDiff * star.angularVelocity / 1000);
        }

star.lastRotation = star.getRotation();
      }
      var stage = new Kinetic.Stage({
        container: 'container',
        width: 578,
        height: 200
      });

var backgroundLayer = new Kinetic.Layer();
      var animatedLayer = new Kinetic.Layer();

var star = new Kinetic.Star({
        x: stage.getWidth() / 2,
        y: stage.getHeight() / 2,
        outerRadius: 80,
        innerRadius: 40,
        stroke: '#005500',
        fill: '#b5ff88',
        strokeWidth: 4,
        numPoints: 5,
        lineJoin: 'round',
        shadowOffset: 5,
        shadowBlur: 10,
        shadowColor: 'black',
        shadowOpacity: 0.5,
        opacity: 0.8
      });

// custom properties
      star.lastRotation = 0;
      star.angularVelocity = 6;
      star.controlled = false;

star.on('mousedown', function(evt) {
        this.angularVelocity = 0;
        this.controlled = true;
      });

animatedLayer.add(star);

var center = new Kinetic.Circle({
        x: stage.getWidth() / 2,
        y: stage.getHeight() / 2,
        radius: 3,
        fill: '#555'
      });

animatedLayer.add(center);

// add listeners to container
      stage.on('mouseup mouseout', function() {
        star.controlled = false;
      });

stage.on('mousemove', function() {
        if(star.controlled) {
          var mousePos = stage.getMousePosition();
          var x = star.getX() - mousePos.x;
          var y = star.getY() - mousePos.y;
          star.setRotation(0.5 * Math.PI + Math.atan(y / x));

if(mousePos.x <= stage.getWidth() / 2) {
            star.rotate(Math.PI);
          }
        }
      });

stage.add(backgroundLayer);
      stage.add(animatedLayer);

// draw background
      var context = backgroundLayer.getContext();
      context.save();
      context.beginPath();
      context.moveTo(stage.getWidth() / 2, stage.getHeight() / 2);
      context.lineTo(stage.getWidth() / 2, stage.getHeight());
      context.strokeStyle = '#555';
      context.lineWidth = 4;
      context.stroke();
      context.restore();

var anim = new Kinetic.Animation(function(frame) {
        animate(animatedLayer, star, frame);
      }, animatedLayer);
      
      // wait one second and then spin the star
      setTimeout(function() {
        anim.start();
      }, 1000)
    </script>
  </body>
</html>

< Interactive Ball Color Picker >

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Modified on February 9th, 2013 by Eric Rowell