function updateRain(context){

		var x = 100;
		var y = 0;
		var R = 0;
		var border = 0;//0-1
		var arpha = 1;
		// setInterval(function(){
		// 	addRains();
		// },300);
		for(var i=0;i<50;i++){
			addRains();
		}
		setInterval(function(){
			context.clearRect(0,0,WINDOW_WIDTH,WINDOW_HEIGHT);
			context.beginPath();
			context.fillStyle = 'rgb(0,5,5)';
			context.fillRect(0,0,WINDOW_WIDTH,WINDOW_HEIGHT);
			rain(context);
		},16)
	}

	//绘制雨滴
	function rain(context){
		for(var i = 0;i<rains.length;i++){
			var _y = rains[i].y;
			var r = 2;
			var arpha = 1
			for(var j = 0;j<50;j++){
				if(_y<=rains[i].surface){
					context.beginPath();
					context.arc(rains[i].x , _y , r , 0 , Math.PI*2 , true);
					context.fillStyle = 'rgba(0,223,223,'+arpha+')';
					context.fill();
					context.closePath();
				}
				_y -= r*1.5;
				r -= 0.04;
				arpha -= 0.02;
			}
			if(rains[i].y>rains[i].surface){
				if(rains[i].waveHr<=1){
					wave(context,i);
					rains[i].waveR += 0.5;
					rains[i].waveHr += 0.005;
					if(rains[i].waveArpha<=0.5){
						rains[i].waveArpha = 0.5
					}else{
						rains[i].waveArpha -= 0.001;
					}
				}else{
					// rains.splice(i,1);
					rains[i] = {
						x:parseInt(Math.random()*WINDOW_WIDTH),
						y:-parseInt(Math.random()*500),
						v:parseInt(Math.random()*6+4),
						rainR:2,
						rainArpha:1,
						waveHr:0,
						waveArpha:1,
						waveR:1,
						surface:WINDOW_HEIGHT - parseInt(50+Math.random()*100)
					}
				}
			}
			rains[i].y += rains[i].v;
		}
	}
	//绘制波纹
	function wave(context,num){
		context.save();
		context.scale(1,0.5);
		context.beginPath();
		var g = context.createRadialGradient(rains[num].x , (rains[num].surface)*2 , 0 , rains[num].x ,(rains[num].surface)*2,rains[num].waveR);
		g.addColorStop(0,'rgba(0,223,223,0)');
		g.addColorStop(rains[num].waveHr,'rgba(0,223,223,0)');
		g.addColorStop(1,'rgba(0,223,223,'+rains[num].waveArpha+')');
		context.fillStyle = g;
		context.arc(rains[num].x,(rains[num].surface)*2,rains[num].waveR,0,Math.PI*2);
		context.fill();
		context.closePath();
		context.restore();
	}

	function addRains(){
		aRain = {
			x:parseInt(Math.random()*WINDOW_WIDTH),
			y:-parseInt(Math.random()*1000),
			v:parseInt(Math.random()*6+4),
			rainR:2,
			rainArpha:1,
			waveHr:0,
			waveArpha:1,
			waveR:1,
			surface:WINDOW_HEIGHT - parseInt(50+Math.random()*100)
		}
		rains.push(aRain);
	}

</script>