<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="robots" content="noindex">
<title>io-fx01</title>
<meta name="author" content="iowen.cn">
<style>
canvas { position: absolute; top: 0; left: 0; }
</style>
</head>
<body>
<canvas id="c" width="1920" height="1040"></canvas>
<script>
var w = c.width = window.innerWidth,
h = c.height = window.innerHeight,
ctx = c.getContext('2d'),
opts = {
len: 20,
count: 50,
baseTime: 10,
addedTime: 10,
dieChance: .05,
spawnChance: 1,
sparkChance: .1,
sparkDist: 10,
sparkSize: 2,
color: 'hsl(hue,100%,light%)',
baseLight: 50,
addedLight: 10,
shadowToTimePropMult: 6,
baseLightInputMultiplier: .01,
addedLightInputMultiplier: .02,
cx: w / 2,
cy: h / 2,
repaintAlpha: .04,
hueChange: .1
},
tick = 0,
lines = [],
dieX = w / 2 / opts.len,
dieY = h / 2 / opts.len,
baseRad = Math.PI * 2 / 6;
ctx.fillStyle = 'black';
ctx.fillRect(0, 0, w, h);
function loop() {
window.requestAnimationFrame(loop); ++tick;
ctx.globalCompositeOperation = 'source-over';
ctx.shadowBlur = 0;
ctx.fillStyle = 'rgba(20,20,20,alp)'.replace('alp', opts.repaintAlpha);
ctx.fillRect(0, 0, w, h);
ctx.globalCompositeOperation = 'lighter';
if (lines.length < opts.count && Math.random() < opts.spawnChance) lines.push(new Line);
lines.map(function(line) {
line.step()
})
}
function Line() {
this.reset()
}
Line.prototype.reset = function() {
this.x = 0;
this.y = 0;
this.addedX = 0;
this.addedY = 0;
this.rad = 0;
this.lightInputMultiplier = opts.baseLightInputMultiplier + opts.addedLightInputMultiplier * Math.random();
this.color = opts.color.replace('hue', tick * opts.hueChange);
this.cumulativeTime = 0;
this.beginPhase()
}
Line.prototype.beginPhase = function() {
this.x += this.addedX;
this.y += this.addedY;
this.time = 0;
this.targetTime = (opts.baseTime + opts.addedTime * Math.random()) | 0;
this.rad += baseRad * (Math.random() < .5 ? 1 : -1);
this.addedX = Math.cos(this.rad);
this.addedY = Math.sin(this.rad);
if (Math.random() < opts.dieChance || this.x > dieX || this.x < -dieX || this.y > dieY || this.y < -dieY) this.reset()
}
Line.prototype.step = function() {++this.time; ++this.cumulativeTime;
if (this.time >= this.targetTime) this.beginPhase();
var prop = this.time / this.targetTime,
wave = Math.sin(prop * Math.PI / 2),
x = this.addedX * wave,
y = this.addedY * wave;
ctx.shadowBlur = prop * opts.shadowToTimePropMult;
ctx.fillStyle = ctx.shadowColor = this.color.replace('light', opts.baseLight + opts.addedLight * Math.sin(this.cumulativeTime * this.lightInputMultiplier));
ctx.fillRect(opts.cx + (this.x + x) * opts.len, opts.cy + (this.y + y) * opts.len, 2, 2);
if (Math.random() < opts.sparkChance) ctx.fillRect(opts.cx + (this.x + x) * opts.len + Math.random() * opts.sparkDist * (Math.random() < .5 ? 1 : -1) - opts.sparkSize / 2, opts.cy + (this.y + y) * opts.len + Math.random() * opts.sparkDist * (Math.random() < .5 ? 1 : -1) - opts.sparkSize / 2, opts.sparkSize, opts.sparkSize)
}
loop();
window.addEventListener('resize',
function() {
w = c.width = window.innerWidth;
h = c.height = window.innerHeight;
ctx.fillStyle = 'black';
ctx.fillRect(0, 0, w, h);
opts.cx = w / 2;
opts.cy = h / 2;
dieX = w / 2 / opts.len;
dieY = h / 2 / opts.len
});
</script>
</body>
</html>
