var i = 1;
var panel;

window.addEvent('domready',function(){
	swappanel();
	$('back').addEvent('click', function(){
		if (i > 1) {
			i--;
			swappanel();
		}
	});
	$('next').addEvent('click', function(){
		if (i < panels) {
			i++;
			swappanel();
		}
	});
});

function swappanel() {
	for (var n = 1; n <= panels; n++) {
		if (n == i) {
			$('panel_'+n).setStyle('display', 'block');
		} else {
			$('panel_'+n).setStyle('display', 'none');
		}
	}
	if (i == panels) {
		$('next').setStyle('visibility', 'hidden');
	} else {
		$('next').setStyle('visibility', 'visible');
	}
	if (i == 1) {
		$('back').setStyle('visibility', 'hidden');
	} else {
		$('back').setStyle('visibility', 'visible');
	}
}