blob: 09e72f222fcafdfa054a2d5a37b1dcc9eca096ca [file] [log] [blame]
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="initial-scale=1.0">
<style>
body {
margin: 0;
}
#stage {
position: relative;
width: 320px;
height: 320px;
border: 1px solid black;
}
.particle {
position: absolute;
height: 20px;
width: 20px;
background-color: blue;
border-radius: 50%;
}
</style>
<script>
function randomInt(min, max)
{
return Math.round(this.random(min, max));
}
function random(min, max)
{
return (Math.random() * (max - min)) + min;
}
function randomColor()
{
var min = 32;
var max = 256 - 32;
return "#"
+ this.randomInt(min, max).toString(16)
+ this.randomInt(min, max).toString(16)
+ this.randomInt(min, max).toString(16);
}
function Point(x, y)
{
this.x = x;
this.y = y;
}
Point.pointOnCircle = function(angle, radius)
{
return new Point(radius * Math.cos(angle), radius * Math.sin(angle));
}
Point.prototype =
{
add: function(other)
{
if(isNaN(other.x))
return new Point(this.x + other, this.y + other);
return new Point(this.x + other.x, this.y + other.y);
},
subtract: function(other)
{
if(isNaN(other.x))
return new Point(this.x - other, this.y - other);
return new Point(this.x - other.x, this.y - other.y);
},
move: function(angle, velocity, timeDelta)
{
return this.add(Point.pointOnCircle(angle, velocity * (timeDelta / 1000)));
},
multiply: function(other)
{
if(isNaN(other.x))
return new Point(this.x * other, this.y * other);
return new Point(this.x * other.x, this.y * other.y);
},
length: function() {
return Math.sqrt( this.x * this.x + this.y * this.y );
},
normalize: function() {
var l = Math.sqrt( this.x * this.x + this.y * this.y );
this.x /= l;
this.y /= l;
return this;
}
}
function Particle(maxPosition)
{
this.element = document.createElement('div');
this.element.className = 'particle';
this.element.style.backgroundColor = randomColor();
this.maxPosition = maxPosition;
this.reset();
this.move();
}
Particle.prototype =
{
reset: function()
{
this.size = new Point(20, 20);
this.maxLocation = this.maxPosition.subtract(this.size);
this.position = new Point(this.maxPosition.x / 2, this.maxPosition.y / 4);
var angle = Math.random() * Math.PI * 2;
this._velocity = new Point(Math.sin(angle), Math.cos(angle)).multiply(random(.8, 1.2));
},
animate: function(timeDelta)
{
this.position = this.position.add(this._velocity.multiply(timeDelta));
this._velocity.y += 0.03;
// If particle is going to move off right side
if (this.position.x > this.maxLocation.x) {
if (this._velocity.x > 0)
this._velocity.x *= -1;
this.position.x = this.maxLocation.x;
} else if (this.position.x < 0) {
// If particle is going to move off left side
if (this._velocity.x < 0)
this._velocity.x *= -1;
this.position.x = 0;
}
// If particle is going to move off bottom side
if (this.position.y > this.maxLocation.y) {
// Adjust direction but maintain magnitude
var magnitude = this._velocity.length();
this._velocity.x *= 1.5 + .005 * this.size.x;
this._velocity = this._velocity.normalize().multiply(magnitude);
if (Math.abs(this._velocity.y) < 0.7)
this.reset();
else {
if (this._velocity.y > 0)
this._velocity.y *= -0.999;
this.position.y = this.maxLocation.y;
}
} else if (this.position.y < 0) {
// If particle is going to move off top side
var magnitude = this._velocity.length();
this._velocity.x *= 1.5 + .005 * this.size.x;
this._velocity = this._velocity.normalize().multiply(magnitude);
if (this._velocity.y < 0)
this._velocity.y *= -0.998;
this.position.y = 0;
}
this.move();
},
move: function()
{
this.element.style.transform = "translate(" + this.position.x + "px," + this.position.y + "px) ";
}
}
var numParticles = 20;
var particles = [];
function makeParticles()
{
var stage = document.getElementById('stage');
var maxPosition = new Point(320, 320);
for (var i = 0; i < numParticles; ++i) {
particles.push(new Particle(maxPosition));
stage.appendChild(particles[i].element);
}
}
function moveParticles()
{
for (var particle of particles)
particle.animate(1);
}
function animate()
{
moveParticles();
window.requestAnimationFrame(animate);
}
function setupAnimation()
{
makeParticles();
animate();
}
window.addEventListener('load', setupAnimation, false);
</script>
</head>
<body>
<div id="stage">
</div>
</body>
</html>