var scrollInt

var scrTime, scrSt, scrDist, scrDur, scrInt, scrSl, scrDistX
function easeInOut(t,b,c,d)

{

    return (c/2*(1-Math.cos(Math.PI*t/d)) + b);

}

scrollPage = function()

{
    scrTime += scrInt
    if (scrTime < scrDur) {

        window.scrollTo(easeInOut(scrTime,scrSl,scrDistX,scrDur), easeInOut(scrTime,scrSt,scrDist,scrDur))

    } else {

        window.scrollTo(scrSl+scrDistX, scrSt+scrDist)
        clearInterval(scrollInt)

    }

}



jQuery.fn.extend({

    smoothScroll : function(duration, velocity, marginLeft, marginTop)

    {

        if(typeof(duration) == 'undefined') duration = 500

        if(typeof(velocity) == 'undefined') velocity = 10

        if(typeof(marginLeft) == 'undefined') marginLeft = 0

        if(typeof(marginTop) == 'undefined') marginTop = 0



        this.click(function(){

            var element_id = $(this).attr("href")

            var source_positions = {

                top : $(this).get(0).offsetTop,

                left : $(this).get(0).offsetLeft

            }

            var dest_positions = {

                top : $(element_id).get(0).offsetTop-marginTop,

                left : $(element_id).get(0).offsetLeft-marginLeft

            }



            if (window.scrollY)

                scrSt = window.scrollY

            else if (document.documentElement.scrollTop)

                scrSt = document.documentElement.scrollTop

            else

                scrSt = document.body.scrollTop

                

            if (window.scrollX)

                scrSl = window.scrollX

            else if (document.documentElement.scrollLeft)

                scrSl = document.documentElement.scrollLeft

            else

                scrSl = document.body.scrollLeft



            scrDist = dest_positions.top - scrSt

            scrDistX = dest_positions.left - scrSl

            scrDur = 500

            scrTime = 0

            scrInt = 5



            // set interval

            clearInterval(scrollInt)

            scrollInt = setInterval(scrollPage, scrInt)



            return false

        })

    }

})