I've just notice a "bug" in the design: The buttons in the menu are not clickable outside of the actual text.
This is a common mistake (I work with that kind of stuff), and it makes the buttons unnecessarily hard to click. Especially when the hover-effect works over all of the button, there is no connection between the visual state and the "clickabillity".
and apply the margins etc. to the span-element instead of the a-element, to force the a-element to completely fill the li-element.