Resource 1
This was a great place to get code for the hamburger buttons, and I also used it during last week's assignment. There's always a lot of options to choose from which are just submitted by random people. They range from very simple to pretty complex, some with JavaScript, but I assume that if you were to copy everything in directly then they would all work fine. However, being contained to the structure of this assignment, some CSS needed modification. It wasn't too difficult, though, as long as I found HTML and JS code with the same structure as the assignment. A decent amount of CSS styling can also have the same effect across multiple elements, so at least you're not limited there.
Resource 2
While I didn't use anything from this site, it was the inspiration for some of my animations like filling the page with the nav or tilting the link hover. The main problems here were that they either use some JavaScript or even different languages for design, but these are some of the coolest menus I've ever seen, hence why it was an inspirational resource. There's a lot of fluid-like/responsive motions for either just the hamburger button or the entire menu, happening either during click or during hover. There's supposed to be 15 on the page, but I only see 10. I think you might have to navigate elsewhere to see the rest. At least it's a little easier to navigate in using the demo and copying code than the first site since you don't have to click into every example.
Resource 3
I don't think I used this site for anything, but I don't think I used any other sites either, so I just include this one since it was one I clicked into. Besides a couple that use JavaScript like we did in the assignment, these are all HTML/CSS only, which is accomplished using checkboxes as far as I can tell. There is a lot of code to sift through at times, but I think some of these examples provide code for most of the page itself instead of just the nav. Also, it's a good research resource because it talks about usage of hamburger menus instead of just providing designs. For example, it talks about hamburger menus being less user-friendly.
Summary
Overall, if you need designs for some widely used website feature, there are probably a decent amount of examples out there. Some definitely require knowing your way around code more than a Front-End 1 student, but at least there's something for all skill levels. Even if you don't need code, you can at least find inspiration to use however you'd like. For this assignment for example, none of the button code was mine except for the modifications I needed to make, but all the menus were my own with just a bit of inspiration.