This was by far one of my favorite resources for this project. I'm surprised by how many different ways you can animate and design a hamburger menu with CSS. This site shows 17 different examples of animating just the menu icons themselves.
Another great resource I found was this site. My favorite thing about it was how straight-forward it was in providing you with the HTML/CSS and a live preview of the code. It's very simple and to-the-point with how to design the menus.
Lastly, I also enjoyed this resource. Like the previous one, it is straight-forward in providing you with the code you need to design the examples, and gives you a live preview result of the code. These menu examples, however, use JavaScript as well. So, this is a resource I probably won't be using until I can learn some JavaScript. Either way, I thought the design of these hamburger menus were very cool and unique.
Ultimately, there are several ways to make and customize hamburger menus. Both the menus themselves, and the three bars you click to open the menu can be customized with CSS animations. These resources showcase multiple varieties of designs.