Here is a screenshot I took, https://www.dropbox.com/s/d6sjrl6oho1bh9z/integral-menu-mobile.PNG?dl=0
Is that what you are referring to?
Reducing the size of your browser is a good way to test mobile responsiveness but it isn’t perfect.
You should test on various devices (mobile phone, tablet, etc.)
But there is a certain break-point where the mobile menu kicks in.
That is part of the Bootstrap Framework with which Integral is built.
This highly depends on how many menu items you have.