I was playing with another version of the menu that comes down from the top. This one uses a slider that resides in a Master slide - but in a layer. Menu is actually the whole slider. When you drag the slider down, everything starts to fade, so you slowly transition into "menu mode".
There is a downside, though, so keep this in mind if you want to use it: if you have any other layers on your slide, those layers will open over the menu layer. So be careful. (I have solution for this - a bit different version of the menu for a later time).
Source attached. Dig around. :)