Drop Down Menu tutorial?!

Ello!

Anyone know where I can find a tutorial that shows how to make drop down menus?

e.g.

Main nav has Home - About Us - Services - Contact as buttons stacked ontop of eachother…

…someone clicks ‘Services’…'Contact button animates down to reveal sub sections of ‘Services’…then when ‘About Us’ is clicked…'Contacts moves up to hide the ‘Services’ sub menus and then 'Services and ‘Contacts’ animate down to reveal sub sections of ‘About Us’!..the again it sub menus hide when other buttons are clicked…does that make sense?

Ive found this one HERE which is just the idea Im after…however does it have to be XML driven?

The one on this site is a bit too basic.

Thanks