var index = 0;
var NUM_PICS = 4;
var DOWNLOAD_URL = "downloads/";
var PIC_PREFIX = "sb";
var PIC_SUFFIX = "_pic";
var PIC_EXT = ".zip";

function dl_nav(dir)
{
	index = index + dir;
	
	if (index < 0) index = NUM_PICS - 1;
	if (index > NUM_PICS - 1) index = 0;
	 document.getElementById("gallery").style.backgroundPosition = -(index * 232) + "px 0";
}

function dl_down()
{
	window.location = DOWNLOAD_URL + PIC_PREFIX + (index + 1) + PIC_SUFFIX + PIC_EXT;
}