Cool menu

Hi

I'm want to know who this menu form this site is done, i mean it is done using action script only.
I know that there are some mcs when the menu is open ,but i dont know how to make the open faze.
If the first button(from the main menu) is open and u click the secon button from the main menu , firss the menu one closes and then the second menu is open.
And the same thing if the second si open and u press the first.

Anyone have an tutorial or an fla will be cool:D

I hope u r not all confuzed my now and please excuse my english

Thank You