var timerArr = new Array();
var topArr = new Array();
var _total = 18;
var c;
var imgSp = 140; //full space for images inc. 119px
var scrollSpeed = 20;

var iSImg = new Array();
for( i = 1; i <= 6; i++ )
{
	iSImg[i] = new Image(); iSImg[i].src=("_imgs/scroll/img"+i+".jpg");
}
var iSImgPool = new Array();
for( i = 1; i <= (_total-6); i++ )
{
	iSImgPool[i] = new Image(); iSImgPool[i].src=("_imgs/scroll/img"+(i+6)+".jpg");
}
var iSImgTemp = new Image();

function imgSwap(divNum){
	c = Math.round(Math.random()/(1/(_total-6)))+1;

	iSImgTemp.src = iSImg[divNum].src;
	iSImg[divNum].src = iSImgPool[c].src;
	iSImgPool[c].src = iSImgTemp.src;

	document.getElementById('ScrollImg'+divNum).src = iSImg[divNum].src;
}

function moveDiv(divNum) {
	topArr[divNum]--;
	document.getElementById('ScrollDiv'+divNum).style.top = (topArr[divNum]+"px");	
	if( document.getElementById('ScrollDiv'+divNum).style.top == "-"+imgSp+"px" ){
		topArr[divNum] = (imgSp*5);
		document.getElementById('ScrollDiv'+divNum).style.top = (imgSp*5)+"px";
		imgSwap(divNum);
	}
}

function move1() { moveDiv(1); }
function move2() { moveDiv(2); }
function move3() { moveDiv(3); }
function move4() { moveDiv(4); }
function move5() { moveDiv(5); }
function move6() { moveDiv(6); }

function scrollStart(){
	for( k = 1; k <= 6; k++ ){
		topArr[k] = (k-1)*imgSp;
		document.getElementById('ScrollDiv'+k).style.top = (topArr[k]+"px");
		imgSwap(k);
	}
	for( i = 1; i <= 6; i++ ){
		timerArr[i] = setInterval(('move'+i+'()'), scrollSpeed);
	}				
}