Adjust Spacing Between Navigation Links

I would like to be able to change the vertical spacing between navigation links when my cover page is viewed on a mobile device.  As you can see there's too little space between my logo and "SCULPTURE" and too much space between the three links.  Is there some CSS code that could allow for these adjustments?  Is it also possible to style the links the same as the action buttons? Where the text is contained in a rectangle that's either a solid color or outline?

here's my cover page:  https://www.joshuakirsch.com

Thanks so much!

Use this CSS to Cover Page Header Injection

<style>
  @media screen and (max-width:767px) {
    ul li {
    	margin-top: 30px !important;
      	margin-bottom: 30px !important;
    }
  }
</style>