This is a slightly modified version of the menu tutorial available here.

It's simple and easy to control / style. Those menus can very quickly get very complex, especially if they have multi-level drop-downs (which you shouldn't really need for the portfolio site). It's mostly CSS with a little bit of jQuery/Java Script for the toggle feature.

Resize the window to see how it behaves. The current breakpoint is set at 768px (if screen is smaller the mobile menu appears).