3D效果的JS烟花背景特效

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
            <html xmlns="http://www.w3.org/1999/xhtml" >
            <head>
            <title>3D效果的JS烟花背景特效丨www.update8.com</title>
            </head>
            <style type="text/css">
            .fire{display:block; overflow:hidden; font-size:12px; position:absolute};
            body{overflow:hidden; background:#000}
            html{overflow:hidden; background:#000}
            </style>
            <body>
            <div style="728px;margin:10px auto; overflow:hidden;">
            <script type="text/javascript">
            </script>
            <script type="text/javascript"
            src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
            </script>
            </div>
            </body>
            <script type="text/javascript">
            var Fire = function(r, color) {
            this.radius = r || 12;
            this.color = color || "FF6600";
            this.xpos = 0;
            this.ypos = 0;
            this.zpos = 0;
            this.vx = 0;
            this.vy = 0;
            this.vz = 0;
            this.mass = 1;
            this.p = document.createElement("span");
            this.p.className = "fire";
            this.p.innerHTML = "*";
            this.p.style.fontSize = this.radius + "px";
            this.p.style.color = "#" + this.color;
            }
            Fire.prototype = {
            append: function(parent) {
            parent.appendChild(this.p);
            },
            setSize: function(scale) {
            this.p.style.fontSize = this.radius * scale + "px";
            },
            setPosition:function(x, y) {
            this.p.style.left = x + "px";
            this.p.style.top = y + "px";
            },
            setVisible: function(b) {
            this.p.style.display = b ? "block" : "none";
            }
            }
            var fireworks = function() {
            var fires = new Array();
            var count = 100;
            var fl = 250;
            var vpx = 500;
            var vpy = 300;
            var gravity = .3;
            var floor = 200;
            var bounce = -.8;
            var timer;
            return {
            init: function() {
            for (var i=0; i<count; i++) {
            var color = 0xFF0000;
            color = (Math.random() * 0xFFFFFF).toString(16).toString().split(".")[0];
            while(color.length < 6) {
            color = "0" + color;
            }
            var fire = new Fire(12, color);
            fires.push(fire);
            fire.ypos = -100;
            fire.vx = Math.random() * 6 - 3;
            fire.vy = Math.random() * 6 - 3;
            fire.vz = Math.random() * 6 - 3;
            fire.append(document.body);
            }
            var that = this;
            timer = setInterval(function() {
            for (var i=0;i<count; i++) {
            that.move(fires[i]);
            }
            }, 30);
            },
            move: function(fire) {
            fire.vy += gravity;
            fire.xpos += fire.vx;
            fire.ypos += fire.vy;
            fire.zpos += fire.vz;
            if (fire.ypos > floor) {
            fire.ypos = floor;
            fire.vy *= bounce;
            }
            if (fire.zpos > -fl) {
            var scale = fl/ (fl+fire.zpos);
            fire.setSize(scale);
            fire.setPosition(vpx + fire.xpos * scale,
            vpy + fire.ypos * scale);
            fire.setVisible(true);
            } else {
            fire.setVisible(false);
            }
            }
            }
            }
            fireworks().init();
            </script>
            </html>