Why doesn't the responsive burger menu open?

Question

css

Help pzhlst deal with the adaptive burger menu.
The menu does not open on the site, the icon is there, but nothing happens when you click. The inspector throws an error: scripts.js:1 Uncaught ReferenceError: $ is not defined at scripts.js:1.
put jQuery in html

<script src="http://code.jquery.com/jquery-latest.min.js"></script>

I uploaded it to the sandbox... Here it surprisingly opens up, BUT when loaded, it immediately shows up open and hides in a second. The html, css, js (jquery) code is the same everywhere.
Please help me understand:
1) why the menu does not open on the site (appears at a resolution of 768px and less))
2) why it is shown open in the sandbox when loading. (I set the resolution large, you can see it right away)
The second day I'm struggling, I can't understand the error. Help out :)

Answer 1

Include jquery BEFORE your script