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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Play Ball</title>
<link rel="stylesheet" href="../include/style.css">
</head>
<body>
<header>
Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a>
</header>
<canvas id="canvas" width="400" height="400"></canvas>
<script src="../include/utils.js"></script>
<script src="./classes/ball.js"></script>
<script src="./classes/segment.js"></script>
<script>
window.onload = function () {
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d'),
ball = new Ball(20),
segments = [],
numSegments = 5,
gravity = 0.5,
bounce = -0.9,
target;
ball.vx = 10;
while (numSegments--) {
segments.push(new Segment(20, 10));
}
//center the last one
segments[segments.length - 1].x = canvas.width / 2;
segments[segments.length - 1].y = canvas.height / 2;
function moveBall () {
ball.vy += gravity;
ball.x += ball.vx;
ball.y += ball.vy;
if (ball.x + ball.radius > canvas.width) {
ball.x = canvas.width - ball.radius;
ball.vx *= bounce;
} else if (ball.x - ball.radius < 0) {
ball.x = ball.radius;
ball.vx *= bounce;
}
if (ball.y + ball.radius > canvas.height) {
ball.y = canvas.height - ball.radius;
ball.vy *= bounce;
} else if (ball.y - ball.radius < 0) {
ball.y = ball.radius;
ball.vy *= bounce;
}
}
function reach (segment, xpos, ypos) {
var dx = xpos - segment.x,
dy = ypos - segment.y;
segment.rotation = Math.atan2(dy, dx);
var w = segment.getPin().x - segment.x,
h = segment.getPin().y - segment.y;
return {
x: xpos - w,
y: ypos - h
};
}
function position (segmentA, segmentB) {
segmentA.x = segmentB.getPin().x;
segmentA.y = segmentB.getPin().y;
}
function checkHit () {
var segment = segments[0],
dx = segment.getPin().x - ball.x,
dy = segment.getPin().y - ball.y,
dist = Math.sqrt(dx * dx + dy * dy);
if (dist < ball.radius) {
ball.vx += Math.random() * 2 - 1;
ball.vy -= 1;
}
}
function move (segment, i) {
if (i !== 0) {
target = reach(segment, target.x, target.y);
position(segments[i - 1], segment);
}
}
function draw (segment) {
segment.draw(context);
}
(function drawFrame () {
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
moveBall();
target = reach(segments[0], ball.x, ball.y);
segments.forEach(move);
checkHit();
segments.forEach(draw);
ball.draw(context);
}());
};
</script>
</body>
</html>