Centering links in menu Options

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Hi guys,
I'm trying to implement some code I found on w3schools for a responsive menu.

This is the code: https://www.w3schools.com/howto/howto_js_to..._responsive.asp

It appears to work well, but the problem I'm having, is that I can't get the links to be centered across the page.
I've tried removing the float: left / adding divs inside divs with percentages / margin: 0 auto, etc. etc., but I'm getting nowhere.

I wonder if someone could help me sort out this problem?

They have a sort of jsfidddle type page here: https://www.w3schools.com/howto/tryit.asp?f...ryhow_js_topnav

Many thanks.