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		<h1>Smooth Scrolling Sticky ScrollSpy Navigation</h1>
		<p><em>Want an explanation of how this works?<br />&rarr; <a href="" target="_top"></a></em></p>
		<section id="introduction">
		<section id="request-response">
			<h2>Request &amp; Response</h2>
		<section id="authentication">
		<section id="endpoints">
			<section id="endpoints--root">
			<section id="endpoints--cities-overview">
				<h3>Cities Overview</h3>
			<section id="endpoints--city-detail">
				<h3>City Detail</h3>
			<section id="endpoints--city-config">
				<h3>City Config</h3>
			<section id="endpoints--city-spots-overview">
				<h3>City Spots Overview</h3>
			<section id="endpoints--city-spot-detail">
				<h3>City Spot Detail</h3>
			<section id="endpoints--city-icons-overview">
				<h3>City Icons Overview</h3>
			<section id="endpoints--city-icon-detail">
				<h3>City Icon Detail</h3>
		<section id="links">
		<section id="expanders">
		<section id="filters">
	<nav class="section-nav">
			<li><a href="#introduction">Introduction</a></li>
			<li><a href="#request-response">Request &amp; Response</a></li>
			<li><a href="#authentication">Authentication</a></li>
			<li><a href="#endpoints">Endpoints</a>
					<li class=""><a href="#endpoints--root">Root</a></li>
					<li class=""><a href="#endpoints--cities-overview">Cities Overview</a></li>
					<li class=""><a href="#endpoints--city-detail">City Detail</a></li>
					<li class=""><a href="#endpoints--city-config">City Config</a></li>
					<li class=""><a href="#endpoints--city-spots-overview">City Spots Overview</a></li>
					<li class=""><a href="#endpoints--city-spot-detail">City Spot Detail</a></li>
					<li class=""><a href="#endpoints--city-icons-overview">City Icons Overview</a></li>
					<li class=""><a href="#endpoints--city-icon-detail">City Icon Detail</a></li>
			<li class=""><a href="#links">Links</a></li>
			<li class=""><a href="#expanders">Expanders</a></li>
			<li class=""><a href="#filters">Filters</a></li>


                /* 1. Enable smooth scrolling */
html {
	scroll-behavior: smooth;

/* 2. Make nav sticky */
main > nav {
	position: sticky;
	top: 2rem;
	align-self: start;

/* 3. ScrollSpy active styles (see JS tab for activation) */
.section-nav > a {
	color: #333;
	font-weight: 500;

/* Sidebar Navigation */
.section-nav {
	padding-left: 0;
	border-left: 1px solid #efefef;

.section-nav a {
	text-decoration: none;
	display: block;
	padding: .125rem 0;
	color: #ccc;
	transition: all 50ms ease-in-out; /* 💡 This small transition makes setting of the active state smooth */

.section-nav a:hover,
.section-nav a:focus {
	color: #666;

/** Poor man's reset **/
* {
	box-sizing: border-box;

html, body {
	background: #fff;

body {
	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;

ul, ol {
	list-style: none;
	margin: 0;
	padding: 0;
li {
	margin-left: 1rem;

h1 {
	font-weight: 300;

/** page layout **/
main {
	display: grid;
	grid-template-columns: 1fr 15em;
	max-width: 100em;
	width: 90%;
	margin: 0 auto;

/** enlarge the sections for this demo, so that we have a long scrollable page **/
section {
	padding-bottom: 20rem;



                window.addEventListener('DOMContentLoaded', () => {

	const observer = new IntersectionObserver(entries => {
		entries.forEach(entry => {
			const id ='id');
			if (entry.intersectionRatio > 0) {
				document.querySelector(`nav li a[href="#${id}"]`).parentElement.classList.add('active');
			} else {
				document.querySelector(`nav li a[href="#${id}"]`).parentElement.classList.remove('active');

	// Track all sections that have an `id` applied
	document.querySelectorAll('section[id]').forEach((section) => {