樱花雨

CSS部分

html, body{
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  overflow: hidden;
}
.container{
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  background-color: #000000;
}

jquery（jquery.min.js）

var RENDERER = {
	INIT_CHERRY_BLOSSOM_COUNT : 30,
	MAX_ADDING_INTERVAL : 10,
	
	init : function(){
		this.setParameters();
		this.reconstructMethods();
		this.createCherries();
		this.render();
	},
	setParameters : function(){
		this.$container = $('#jsi-cherry-container');
		this.width = this.$container.width();
		this.height = this.$container.height();
		this.context = $('').attr({width : this.width, height : this.height}).appendTo(this.$container).get(0).getContext('2d');
		this.cherries = [];
		this.maxAddingInterval = Math.round(this.MAX_ADDING_INTERVAL * 1000 / this.width);
		this.addingInterval = this.maxAddingInterval;
	},
	reconstructMethods : function(){
		this.render = this.render.bind(this);
	},
	createCherries : function(){
		for(var i = 0, length = Math.round(this.INIT_CHERRY_BLOSSOM_COUNT * this.width / 1000); i < length; i++){
			this.cherries.push(new CHERRY_BLOSSOM(this, true));
		}
	},
	render : function(){
		requestAnimationFrame(this.render);
		this.context.clearRect(0, 0, this.width, this.height);
		
		this.cherries.sort(function(cherry1, cherry2){
			return cherry1.z - cherry2.z;
		});
		for(var i = this.cherries.length - 1; i >= 0; i--){
			if(!this.cherries[i].render(this.context)){
				this.cherries.splice(i, 1);
			}
		}
		if(--this.addingInterval == 0){
			this.addingInterval = this.maxAddingInterval;
			this.cherries.push(new CHERRY_BLOSSOM(this, false));
		}
	}
};
var CHERRY_BLOSSOM = function(renderer, isRandom){
	this.renderer = renderer;
	this.init(isRandom);
};
CHERRY_BLOSSOM.prototype = {
	FOCUS_POSITION : 300,
	FAR_LIMIT : 600,
	MAX_RIPPLE_COUNT : 100,
	RIPPLE_RADIUS : 100,
	SURFACE_RATE : 0.5,
	SINK_OFFSET : 20,
	
	init : function(isRandom){
		this.x = this.getRandomValue(-this.renderer.width, this.renderer.width);
		this.y = isRandom ? this.getRandomValue(0, this.renderer.height) : this.renderer.height * 1.5;
		this.z = this.getRandomValue(0, this.FAR_LIMIT);
		this.vx = this.getRandomValue(-2, 2);
		this.vy = -2;
		this.theta = this.getRandomValue(0, Math.PI * 2);
		this.phi = this.getRandomValue(0, Math.PI * 2);
		this.psi = 0;
		this.dpsi = this.getRandomValue(Math.PI / 600, Math.PI / 300);
		this.opacity = 0;
		this.endTheta = false;
		this.endPhi = false;
		this.rippleCount = 0;
		
		var axis = this.getAxis(),
			theta = this.theta + Math.ceil(-(this.y + this.renderer.height * this.SURFACE_RATE) / this.vy) * Math.PI / 500;
		theta %= Math.PI * 2;
		
		this.offsetY = 40 * ((theta <= Math.PI / 2 || theta >= Math.PI * 3 / 2) ? -1 : 1);
		this.thresholdY = this.renderer.height / 2 + this.renderer.height * this.SURFACE_RATE * axis.rate;
		this.entityColor = this.renderer.context.createRadialGradient(0, 40, 0, 0, 40, 80);
		this.entityColor.addColorStop(0, 'hsl(330, 70%, ' + 50 * (0.3 + axis.rate) + '%)');
		this.entityColor.addColorStop(0.05, 'hsl(330, 40%,' + 55 * (0.3 + axis.rate) + '%)');
		this.entityColor.addColorStop(1, 'hsl(330, 20%, ' + 70 * (0.3 + axis.rate) + '%)');
		this.shadowColor = this.renderer.context.createRadialGradient(0, 40, 0, 0, 40, 80);
		this.shadowColor.addColorStop(0, 'hsl(330, 40%, ' + 30 * (0.3 + axis.rate) + '%)');
		this.shadowColor.addColorStop(0.05, 'hsl(330, 40%,' + 30 * (0.3 + axis.rate) + '%)');
		this.shadowColor.addColorStop(1, 'hsl(330, 20%, ' + 40 * (0.3 + axis.rate) + '%)');
	},
	getRandomValue : function(min, max){
		return min + (max - min) * Math.random();
	},
	getAxis : function(){
		var rate = this.FOCUS_POSITION / (this.z + this.FOCUS_POSITION),
			x = this.renderer.width / 2 + this.x * rate,
			y = this.renderer.height / 2 - this.y * rate;
		return {rate : rate, x : x, y : y};
	},
	renderCherry : function(context, axis){
		context.beginPath();
		context.moveTo(0, 40);
		context.bezierCurveTo(-60, 20, -10, -60, 0, -20);
		context.bezierCurveTo(10, -60, 60, 20, 0, 40);
		context.fill();
		
		for(var i = -4; i < 4; i++){
			context.beginPath();
			context.moveTo(0, 40);
			context.quadraticCurveTo(i * 12, 10, i * 4, -24 + Math.abs(i) * 2);
			context.stroke();
		}
	},
	render : function(context){
		var axis = this.getAxis();
		
		if(axis.y == this.thresholdY && this.rippleCount < this.MAX_RIPPLE_COUNT){
			context.save();
			context.lineWidth = 2;
			context.strokeStyle = 'hsla(0, 0%, 100%, ' + (this.MAX_RIPPLE_COUNT - this.rippleCount) / this.MAX_RIPPLE_COUNT + ')';
			context.translate(axis.x + this.offsetY * axis.rate * (this.theta <= Math.PI ? -1 : 1), axis.y);
			context.scale(1, 0.3);
			context.beginPath();
			context.arc(0, 0, this.rippleCount / this.MAX_RIPPLE_COUNT * this.RIPPLE_RADIUS * axis.rate, 0, Math.PI * 2, false);
			context.stroke();
			context.restore();
			this.rippleCount++;
		}
		if(axis.y < this.thresholdY || (!this.endTheta || !this.endPhi)){
			if(this.y <= 0){
				this.opacity = Math.min(this.opacity + 0.01, 1);
			}
			context.save();
			context.globalAlpha = this.opacity;
			context.fillStyle = this.shadowColor;
			context.strokeStyle = 'hsl(330, 30%,' + 40 * (0.3 + axis.rate) + '%)';
			context.translate(axis.x, Math.max(axis.y, this.thresholdY + this.thresholdY - axis.y));
			context.rotate(Math.PI - this.theta);
			context.scale(axis.rate * -Math.sin(this.phi), axis.rate);
			context.translate(0, this.offsetY);
			this.renderCherry(context, axis);
			context.restore();
		}
		context.save();
		context.fillStyle = this.entityColor;
		context.strokeStyle = 'hsl(330, 40%,' + 70 * (0.3 + axis.rate) + '%)';
		context.translate(axis.x, axis.y + Math.abs(this.SINK_OFFSET * Math.sin(this.psi) * axis.rate));
		context.rotate(this.theta);
		context.scale(axis.rate * Math.sin(this.phi), axis.rate);
		context.translate(0, this.offsetY);
		this.renderCherry(context, axis);
		context.restore();
		
		if(this.y <= -this.renderer.height / 4){
			if(!this.endTheta){
				for(var theta = Math.PI / 2, end = Math.PI * 3 / 2; theta <= end; theta += Math.PI){
					if(this.theta < theta && this.theta + Math.PI / 200 > theta){
						this.theta = theta;
						this.endTheta = true;
						break;
					}
				}
			}
			if(!this.endPhi){
				for(var phi = Math.PI / 8, end = Math.PI * 7 / 8; phi <= end; phi += Math.PI * 3 / 4){
					if(this.phi < phi && this.phi + Math.PI / 200 > phi){
						this.phi = Math.PI / 8;
						this.endPhi = true;
						break;
					}
				}
			}
		}
		if(!this.endTheta){
			if(axis.y == this.thresholdY){
				this.theta += Math.PI / 200 * ((this.theta < Math.PI / 2 || (this.theta >= Math.PI && this.theta < Math.PI * 3 / 2)) ? 1 : -1);
			}else{
				this.theta += Math.PI / 500;
			}
			this.theta %= Math.PI * 2;
		}
		if(this.endPhi){
			if(this.rippleCount == this.MAX_RIPPLE_COUNT){
				this.psi += this.dpsi;
				this.psi %= Math.PI * 2;
			}
		}else{
			this.phi += Math.PI / ((axis.y == this.thresholdY) ? 200 : 500);
			this.phi %= Math.PI;
		}
		if(this.y <= -this.renderer.height * this.SURFACE_RATE){
			this.x += 2;
			this.y = -this.renderer.height * this.SURFACE_RATE;
		}else{
			this.x += this.vx;
			this.y += this.vy;
		}
		return this.z > -this.FOCUS_POSITION && this.z < this.FAR_LIMIT && this.x < this.renderer.width * 1.5;
	}
};
$(function(){
	RENDERER.init();
});