var divMainText;
var imgMainButton;
var tHandle;
var hiddenText;
var startPos = 420;
var endPos = 555;
var offset = 20;

function main() {
	divMainText = document.getElementById('mainText');
	imgMainButton = document.getElementById('mainButton');
	hiddenText = document.getElementById('hiddenText')
	imgMainButton.onmouseover = function(){this.src = '/img/forward_blue.png';};
	imgMainButton.onmouseout = function(){this.src = '/img/forward_red.png';};
	imgMainButton.onclick = forward;
}

function forward() {
	hiddenText.style.display = 'block';
	tHandle = window.setInterval(down,40);
}

function down() {
	if((divMainText.clientHeight - offset) < endPos) {
		divMainText.style.height = divMainText.clientHeight-offset+20+'px';
	}
	else {
		window.clearInterval(tHandle);
		imgMainButton.src = 'img/hide_red.png';
		imgMainButton.onmouseover = function(){this.src = '/img/hide_blue.png';};
		imgMainButton.onmouseout = function(){this.src = '/img/hide_red.png';};
		imgMainButton.onclick = back;
	}
}

function back() {
	tHandle = window.setInterval(up,40)
}

function up() {
	if((divMainText.clientHeight-offset) > startPos) {
		divMainText.style.height = divMainText.clientHeight-offset-20+'px';		
	}
	else {
		window.clearInterval(tHandle);
		hiddenText.style.display = 'none';
		imgMainButton.src = 'img/forward_red.png';
		imgMainButton.onmouseover = function(){this.src = '/img/forward_blue.png';};
		imgMainButton.onmouseout = function(){this.src = '/img/forward_red.png';};
		imgMainButton.onclick = forward;
	}

}