http://assets.tumblr.com/javascript/pinned.js

pinned.js

Event.observe(window, 'dom:loaded', function () {
	$$('.post .pin').each(function (pin) {
		var up, down;
		Event.observe(pin, 'mouseenter', function (event) {
			clearInterval(down);
			var step = 1;
			up = window.setInterval(function () {
				if (step == 11) {
					clearInterval(up);
					return
				}
				pin.addClassName('step_' + step);
				step++
			},
			10)
		});
		Event.observe(pin, 'mouseleave', function (event) {
			clearInterval(up);
			var step = 10;
			down = window.setInterval(function () {
				if (step == 1) {
					clearInterval(down);
					return
				}
				pin.removeClassName('step_' + step);
				step--
			},
			10)
		});
		Event.observe(pin, 'click', function (event) {
			clearInterval(up);
			clearInterval(down);
			Event.stopObserving(pin);
			pin.addClassName('unpinned');
			var post = pin.up('li');
			var clone = post.cloneNode(false);
			clone.removeClassName('promotion_pinned').addClassName('promotion_pinned_clone');
			var bottom_margin = parseInt(post.getStyle('marginBottom'), 10) ? 10 : 0;
			clone.style.height = post.getHeight() + parseInt(post.getStyle('marginTop'), 10) + bottom_margin + 'px';
			post.addClassName('unpinned');
			post.insert({
				after: clone
			});
			var form_key = $('form_key') && $('form_key').value;
			new Ajax.Request('/unpin', {
				method: 'post',
				parameters: {
					post_id: post.id.replace('post_', ''),
					form_key: form_key
				}
			});
			setTimeout(function () {
				post.addClassName('falloff');
				setTimeout(function () {
					post.addClassName('falloff_animated');
					clone.addClassName('collapse');
					setTimeout(function () {
						post.remove()
					},
					800);
					setTimeout(function () {
						clone.remove()
					},
					2000)
				},
				0)
			},
			300)
		})
	})
});