Embedded Video over main navigation

Hi guys,

On the frontpage of our website we have a slider with just one single slide. It consists of a picture and an embedded video, so there’s a play button.
Here’s a screenshot: http://vcrp4.vcrp.de/f/f8f44ae8f0/
When I click the button the video starts, but it’s “under” the main navigation on the top.
This issue irritates the user, so I’d like to hide the navigation whenever the video starts or just make the video frame small enough.

Is there a way to do it?

Many thanks in advance!