How to fix a node.js error in the HTML5 game tutorial

//set main namespace
goog.provide('treehouse');
goog.require('lime.Director');
goog.require('lime.Scene');
goog.require('lime.Sprite');
goog.require('treehouse.Frog');

//constants for directions
var NORTH = 1;
var EAST = 2;
var SOUTH = 3;
var WEST = 4;

// entrypoint
treehouse.start = function(){

    //set the main lime objects for the game
    this.lime=lime;
    this.director = new this.lime.Director(document.body,1600,780);
    this.director.makeMobileWebAppCapable();
    this.director.setDisplayFPS(false);
    this.gameScene = new this.lime.Scene();
    this.gameScene.setRenderer(this.lime.Renderer.CANVAS);

    //set the main game objects
    var gameBackground = new this.lime.Sprite()
        .setSize(1080,780)
        .setPosition(0,0)
        .setFill("#EEEEEE")
        .setAnchorPoint(0,0);
    this.frog = new treehouse.Frog ();
    this.walls = [];
    this.badges = [];
    this.createWalls();
    this.createBadges();
    //this.positionBadgesAndFrog();
    //this.badgesEarned = 0;

     // create game buttons
    var analogStick = new this.lime.Sprite().setSize(350,372).setPosition(1150,400).setFill('img/analogStick.png').setAnchorPoint(0,0);
    var buttonUp = new this.lime.Sprite().setSize(120,120).setPosition(1265,400).setAnchorPoint(0,0);
    var buttonRight = new this.lime.Sprite().setSize(115,114).setPosition(1384,518).setAnchorPoint(0,0);
    var buttonDown = new this.lime.Sprite().setSize(120,120).setPosition(1265,631).setAnchorPoint(0,0);
    var buttonLeft = new this.lime.Sprite().setSize(115,114).setPosition(1151,518).setAnchorPoint(0,0);

    //add objects to the main game scene
    this.gameScene.appendChild(gameBackground);
    for (var i=0;i<this.walls.length;i++) {
    this.gameScene.appendChild(this.walls[i]);
    }
  for (i=0;i<this.badges.length;i++) {
    this.gameScene.appendChild(this.badges[i]);
    }
    this.gameScene.appendChild(this.frog);
    this.gameScene.appendChild(analogStick);
    this.gameScene.appendChild(buttonUp);
    this.gameScene.appendChild(buttonRight);
    this.gameScene.appendChild(buttonDown);
    this.gameScene.appendChild(buttonLeft);

    // set the scene
  this.director.replaceScene(this.gameScene);

};

    treehouse.createWalls = function() {
    t=30
    var walls = [];
    var wallCoordinates = [
        [0,0,35*t,t],
        [0,0,t,26*t],
        [35*t,0,36*t,26*t],
        [0,25*t,36*t,35*t],
        [0,25*t,36*t,35*t],
        [0,10*t,5*t,11*t],
        [5*t,5*t,16*t,6*t],
        [15*t,5*t,16*t,11*t],
        [15*t,5*t,16*t,11*t],
        [15*t,10*t,21*t,11*t],
        [20*t,10*t,21*t,16*t],
        [5*t,15*t,21*t,16*t],
        [10*t,10*t,11*t,16*t],
        [5*t,20*t,11*t,21*t],
        [5*t,20*t,6*t,26*t],
        [15*t,15*t,16*t,26*t],
        [20*t,0*t,21*t,6*t],
        [25*t,5*t,36*t,6*t],
        [25*t,5*t,26*t,11*t],
        [30*t,10*t,36*t,11*t],
        [30*t,10*t,31*t,16*t],
        [25*t,15*t,30*t,16*t],
        [25*t,15*t,26*t,20*t],
        [20*t,20*t,26*t,21*t],
        [30*t,20*t,31*t,26*t]
    ];
        for (var i=0;i<wallCoordinates.length;i++) {
            var current = wallCoordinates[i];
        this.lime.Sprite().setAnchorPoint(0,0).setPosition(current[0],current[1]).setSize(current[2]-current[0],current[3]-current[1]).setFill('#222222');
        this.walls.push(wall);
    }
};

    //this is required for outside access after code is compiled in ADVANCED_COMPILATIONS mode
goog.exportSymbol('treehouse.start', treehouse.start);