Javascript-форум - В чём ошибка?

Хочу подключить скрипт на сайт, но он выводит ошибку в 12 строке, что не так?
window.requestAnimFrame = (function(){
 return window.requestAnimationFrame ||
 window.webkitRequestAnimationFrame ||
 window.mozRequestAnimationFrame ||
 window.oRequestAnimationFrame ||
 window.msRequestAnimationFrame ||
 function( callback ){
 window.setTimeout(callback, 1000 / 60);
 };
})();
var canvas = document.getElementById('cvs'),
 ctx = canvas.getContext('2d'),
 height = canvas.height = document.body.offsetHeight,
 width = canvas.width = document.body.offsetWidth,
 collection = [],
 num_drops = 2000,
 gravity = 1,
 windforce = 1,
 windmultiplier = 0,
 gutter = 0;

function Drop() {
 this.x;
 this.y;
 this.radius;
 this.distance;
 this.color;
 this.speed;
 this.vx;
 this.vy;
}
Drop.prototype = {
 constructor: Drop,

 random_x: function() {
 var n = width * (1 + gutter);
 return (1 - (1 + gutter)) + (Math.random() * n);
 },
 draw: function(ctx) {
 ctx.fillStyle = this.color;
 ctx.beginPath();
 ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false);
 ctx.closePath();
 ctx.fill();
 }
};

function draw_frame() {

ctx.clearRect(0, 0, width, height);
 collection.forEach(function (drop) {
 ctx.globalAlpha = (drop.distance + 1) / 10;
 drop.draw(ctx);
 ctx.globalAlpha = 1;
 drop.x += drop.vx;
 drop.y += drop.vy;
 var lx = drop.vx + windforce;
 lx < maxspeed && lx > 1 - maxspeed && (drop.vx = lx);
 if (drop.y > (drop.distance + 1) / 10 * height) {
 drop.y = Math.random() * -drop.radius * (num_drops / 10);
 drop.x = drop.random_x();
 }
 if (drop.x > width * (1 + gutter)) {
 drop.x = 1 - (width * gutter);
 }
 if (drop.x < 1 - (width * gutter)) {
 drop.x = width * (1 + gutter);
 }
 });
}

function animate() {
 requestAnimFrame(animate);
 draw_frame();
}

function windtimer() {
 windforce = Math.random() > 0.5 ? windmultiplier : -windmultiplier;
 setTimeout(windtimer, Math.random() * (1000 * 30));
}

function init() {
 collection = [];
 while (num_drops--) {
 var drop = new Drop(); // todo: make constructor do this shit
 drop.color = "#eee";
 drop.distance = Math.random() * 10 | 0;
 drop.speed = Math.random() * (drop.distance / 10) + gravity;
 drop.vx = 0;
 drop.vy = Math.random() * drop.speed + (drop.speed / 2);
 drop.radius = (drop.distance + 1) / 16 * 3;
 drop.x = drop.random_x();
 drop.y = Math.random() * height;
 collection.push(drop);
 }
 windtimer();
 animate();
 window.onresize = function() {
 height = canvas.height = document.body.offsetHeight;
 width = canvas.width = document.body.offsetWidth;
 };
}
init();