var cheight = 0;
var maxSize = 120;
var dw = 1;
var timerRunning = false;
var timerID;

function slide(){
	if(timerRunning)
		clearTimeout(timerID);
	timerRunning = false;
	dw = -dw ;
	timerRunning = true;
	timerID = self.setTimeout("ping()", 10);
}

function grow(){
	dw = 1 ;
	timerRunning = true;
	timerID = self.setTimeout("ping()", 10);
}

function ping(){
	if(!timerRunning) return;
	if(dw > 0){
		cheight -= 20;
		if(cheight <= 0){
			cheight = 0;
			if(timerRunning)
				clearTimeout(timerID);
			timerRunning = false;
		}else{
			timerID = self.setTimeout("ping()", 10);
		}
		document.getElementById('box').style.height = cheight + 'px';
	}else if(dw < 0){
		cheight += 20;
		if(cheight >= maxSize){
			cheight = maxSize;
			if(timerRunning)
				clearTimeout(timerID);
			timerRunning = false;
		}else{
			timerID = self.setTimeout("ping()", 10);
		}
		document.getElementById('box').style.height = cheight + 'px';
	} else {
		if(timerRunning)
			clearTimeout(timerID);
		timerRunning = false;
	}
}