var actT = 1;

var TimeID;
var scry,dy,y,iniy,viewy;

function Init(){
dy = 0;
y = 0;
iniy = 0;
viewy = iniy;
}

function up(rq){
scry = rq;
iniy = viewy;
dy = 0;
y = 0;
scroll_up();
}

function down(rq){
scry = rq;
iniy = viewy;
dy = 0;
y = 0;
scroll_down();
}

function topdown(rq){
scry = rq;
iniy = viewy = 0;
dy = 0;
y = 0;
scroll_down();
}

function scroll_down(){
var tgty = iniy + scry;
if( y < (scry/2) ){
dy++;
}else if( y > (scry/2) ){
dy--;
dy = Math.max(dy , 1);
}
y += dy;
viewy = iniy + y;
viewy = Math.min( viewy , tgty );
self.scroll(0,viewy);
if(viewy >= tgty){
clearTimeout(TimeID);
}else{
TimeID = setTimeout( "scroll_down()" , actT);
}
}

function scroll_up(){
var tgty = iniy - scry;
if( y < (scry/2) ){
dy++;
}else if( y > (scry/2) ){
dy--;
dy = Math.max(dy , 1);
}
y += dy;
viewy = iniy - y;
viewy = Math.max( viewy , tgty );
self.scroll(0,viewy);
if(viewy <= tgty){
clearTimeout(TimeID);
}else{
TimeID = setTimeout( "scroll_up()" , actT);
}
}