HTMLThis is the HTML for the entire page.
You have to note a few important things. The navigation icon has the 'mobile-inner-header-icon-out' class attached to it, this class is important for the animation of the icon. Another important thing is that there are two 'span' divs inside the header icon. Those will be the lines that animate when you click on them.
CSSThere are other CSS styles that are related to '.mobile-inner-nav a' which you can find inside 'main.css' file. You will find the styles that animate the link embedded inside this document.
You can see that '.mobile-inner-nav a' has the animations 'returnToNormal' appointed to it.