scrolling content in a div with jQuery - scroll

Question

I'm trying to scroll content vertically in a div. However, I would like it to loop, so that when the last item in the div reaches the top of the container, the first items follow it, and if the first item is already at the top of my container, I don't want the previous button to work, but I'm not sure how to do either of these two things. Any help would be appreciated.
JSFIDDLE
HTML
<div class="container">
<div class="block block-1">1</div>
<div class="block block-2">2</div>
<div class="block block-3">3</div>
<div class="block block-4">4</div>
<div class="block block-5">5</div>
<div class="block block-6">6</div>
</div>
<button id="prev">Previous</button>
<button id="next">Next</button>
jQuery
$( "#prev" ).click(function()
{
$( ".block" ).animate({ "top": "+=50px" }, "slow" );
});
$( "#next" ).click(function()
{
$( ".block" ).animate({ "top": "-=50px" }, "slow" );
});
CSS
.container
{
position: relative;
background-color: #f5f5f5;
width: 590px;
height: 330px;
overflow: hidden;
font-family: arial, sans;
font-weight: bold;
text-align: center;
margin-bottom: 20px;
}
.block
{
position: absolute;
width: 90px;
height: 90px;
color: #fff;
}
.block-1
{
background-color: #900;
}
.block-2
{
top: 100px;
background-color: #090;
}
.block-3
{
top: 200px;
background-color: #009;
}
.block-4
{
top: 300px;
background-color: #990;
}
.block-5
{
top: 400px;
background-color: #909;
}
.block-6
{
top: 500px;
background-color: #099;
}

Answer 1

If you want it to loop, you can do a test where every time a div's vertical position goes out of bounds, it gets moved to the bottom of the pile, and reverse this when scrolling up. Essentially you just cut and paste the elements in the right order using $.remove(), $.append(), $.clone().