Responsive page with navigation toggle made with CSS Grid and JS

The navigation menu toggle was fun to make. Using the aria-expanded attribute I was able to work in a ternary expression and use classList.toggle(). My grid layouts are still a little wonky but I am getting more comfortable and faster at implementing CSS Grid.

My overlay that shadows out the body content when the expanded navigation menu is open only covers the header section. I wondered if there is a way to freeze the rest of the page from scrolling when the menu is showing.

Let me know what you think of my solution. All and any feedback is welcome!