mind-overflow-website-ghost-theme/assets/js/arrow-fade.js

// JavaScript Document
$(document).ready(function(){
	$(window).scroll(function(){
		if($(this).scrollTop() > $(window).height()*0.3){
			$(".arrow-down").css({"opacity" : "0"});
		} else {
			$(".arrow-down").css({"opacity" : "0.4"});
		}
	})
})