How do I hide my navigation menu on an Index page?

Hi all, I want to hide my primary and secondary nav on the following Index page of my site. https://mandarin-lilac-j8jw.squarespace.com/yc-landing-page I tried a bunch of header-code injection(s) and nothing seemed to work. Template is Brine. Please advise! 

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Add this to the Index's code injection. It will hide the navigation, but keep the logo visible.

<style>
.Header-nav {
      display:none !important;
      }
</style>