function semicircleTransition(t) {
	return Math.sin(t * Math.PI);
}

function spinBrackets() {
	var distance = $('right-bracket').offsetLeft - $('left-bracket').offsetLeft; // - $('left-bracket').offsetWidth/2;
	new Effect.Parallel([
		new Effect.Move('left-bracket', {sync: true, x: distance/2, y: 0, transition: semicircleTransition}),
		new Effect.Move('right-bracket', {sync: true, x: -distance/2, y: 0, transition: semicircleTransition})
	], {duration: 1.5, afterFinish: spinBrackets});
}

function showFeedbackForm(url) {
	new Effect.Appear('feedback-form', {duration: 0.3});
	$('feedback-frame').src = url;
}

function hideFeedbackForm() {
	new Effect.Fade('feedback-form', {duration: 0.3});
}