Option to remove horizontal line on header

[trangnv]

Hi, I am using this theme to create a personal web page. It's great, I love it.
But 1 thing I've tried to remove but haven't figured out how is a horizontal line on header.
Appreciate any help

[trangnv]

found it
https://github.com/pages-themes/hacker/blob/master/_sass/jekyll-theme-hacker.scss#L57