jQuery.timer = function (interval, callback) {
    var interval = interval || 100;
    if (!callback)
        return false;
        _timer = function (interval, callback) {
        this.stop = function () {
            clearInterval(self.id);
        };
        
        this.internalCallback = function () {
            callback(self);
        };
        
        this.reset = function (val) {
            if (self.id)
                clearInterval(self.id);
            
            var val = val || 100;
            this.id = setInterval(this.internalCallback, val);
        };
        
        this.interval = interval;
        this.id = setInterval(this.internalCallback, this.interval);
        
        var self = this;
    };
    return new _timer(interval, callback);
};

// see: http://stackoverflow.com/questions/210717/using-jquery-to-center-a-div-on-the-screen
jQuery.fn.center = function () {
    this.css("position","absolute");
    this.css("top", (($(window).height() - this.outerHeight()) / 2) + $(window).scrollTop() + "px");
    this.css("left", (($(window).width() - this.outerWidth()) / 2) + $(window).scrollLeft() + "px");
    return this;
}

function log(str) {    
    //firebug running
    if('object' == typeof console) {
        console.log(str);
    }
}  

function simple_moving_averager(period) {
    var nums = [];
    return function(num) {
        nums.push(num);
        if (nums.length > period)
            nums.splice(0,1);  // remove the first element of the array
        var sum = 0;
        for (var i in nums)
            sum += nums[i];
        var n = period;
        if (nums.length < period)
            n = nums.length;
        return(sum/n);
    }
}