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function snowFall(snow) {
snow = snow || {};
this.maxFlake = snow.maxFlake || 200;
this.flakeSize = snow.flakeSize || 10;
this.fallSpeed = snow.fallSpeed || 1;
}
requestAnimationFrame = window.requestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.msRequestAnimationFrame ||
window.oRequestAnimationFrame ||
function(callback) { setTimeout(callback, 1000 / 60); };
cancelAnimationFrame = window.cancelAnimationFrame ||
window.mozCancelAnimationFrame ||
window.webkitCancelAnimationFrame ||
window.msCancelAnimationFrame ||
window.oCancelAnimationFrame;
snowFall.prototype.start = function(){
snowCanvas.apply(this);
createFlakes.apply(this);
drawSnow.apply(this)
}
function snowCanvas() {
var snowcanvas = document.createElement("canvas");
snowcanvas.id = "snowfall";
snowcanvas.width = window.innerWidth;
snowcanvas.height = document.body.clientHeight;
snowcanvas.setAttribute("style", "position:absolute; top: 0; left: 0; z-index: 1; pointer-events: none;");
document.getElementsByTagName("body")[0].appendChild(snowcanvas);
this.canvas = snowcanvas;
this.ctx = snowcanvas.getContext("2d");
window.onresize = function() {
snowcanvas.width = window.innerWidth;
}
}
function flakeMove(canvasWidth, canvasHeight, flakeSize, fallSpeed) {
this.x = Math.floor(Math.random() * canvasWidth);
this.y = Math.floor(Math.random() * canvasHeight);
this.size = Math.random() * flakeSize + 2;
this.maxSize = flakeSize;
this.speed = Math.random() * 1 + fallSpeed;
this.fallSpeed = fallSpeed;
this.velY = this.speed;
this.velX = 0;
this.stepSize = Math.random() / 30;
this.step = 0
}
flakeMove.prototype.update = function() {
var x = this.x,
y = this.y;
this.velX *= 0.98;
if (this.velY <= this.speed) {
this.velY = this.speed
}
this.velX += Math.cos(this.step += .05) * this.stepSize;
this.y += this.velY;
this.x += this.velX;
if (this.x >= canvas.width || this.x <= 0 || this.y >= canvas.height || this.y <= 0) {
this.reset(canvas.width, canvas.height)
}
};
flakeMove.prototype.reset = function(width, height) {
this.x = Math.floor(Math.random() * width);
this.y = 0;
this.size = Math.random() * this.maxSize + 2;
this.speed = Math.random() * 1 + this.fallSpeed;
this.velY = this.speed;
this.velX = 0;
};
flakeMove.prototype.render = function(ctx) {
var snowFlake = ctx.createRadialGradient(this.x, this.y, 0, this.x, this.y, this.size);
snowFlake.addColorStop(0, "rgba(255, 255, 255, 0.9)");
snowFlake.addColorStop(.5, "rgba(255, 255, 255, 0.5)");
snowFlake.addColorStop(1, "rgba(255, 255, 255, 0)");
ctx.save();
ctx.fillStyle = snowFlake;
ctx.beginPath();
ctx.arc(this.x, this.y, this.size, 0, Math.PI * 2);
ctx.fill();
ctx.restore();
};
function createFlakes() {
var maxFlake = this.maxFlake,
flakes = this.flakes = [],
canvas = this.canvas;
for (var i = 0; i < maxFlake; i++) {
flakes.push(new flakeMove(canvas.width, canvas.height, this.flakeSize, this.fallSpeed))
}
}
function drawSnow() {
var maxFlake = this.maxFlake,
flakes = this.flakes;
ctx = this.ctx, canvas = this.canvas, that = this;
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (var e = 0; e < maxFlake; e++) {
flakes[e].update();
flakes[e].render(ctx);
}
this.loop = requestAnimationFrame(function() {
drawSnow.apply(that);
});
}
var snow = new snowFall({maxFlake:60});
snow.start();
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