<pre style="word-wrap: break-word; white-space: pre-wrap;">  &lt;!DOCTYPE html&gt;
&lt;html lang="en"&gt;
    &lt;head&gt;
        &lt;meta charset="UTF-8" /&gt;
        &lt;meta http-equiv="X-UA-Compatible" content="IE=edge" /&gt;
        &lt;meta name="viewport" content="width=device-width, initial-scale=1.0" /&gt;
        &lt;title&gt;Document&lt;/title&gt;

        &lt;style&gt;
            .primary-header {
                --_bg: hsl(0 0% 100%);
                --_logo-color: hsl(0, 0%, 5%);
                --_nav-link-color: hsl(37, 82%, 20%);

                padding: 1rem;
                background: var(--_bg);

                position: sticky;
                top: 0;
            }

            /* for demo, probably not the best idea */
            .primary-header,
            .primary-header * {
                transition: 500ms;
            }

            .primary-header.sticking {
                --_bg: #333;
                --_logo-color: #fff;
                --_nav-link-color: #f00;
            }

            .primary-header__inner {
                display: flex;
                justify-content: space-between;
            }

            .primary-header a {
                color: var(--_nav-link-color);
            }

            .primary-header a:hover,
            .primary-header a:focus {
                opacity: 0.7;
            }

            .logo {
                color: var(--_logo-color);
            }

            .nav-list {
                list-style: none;
                margin: 0;
                padding: 0;

                display: flex;
                gap: clamp(0.5rem, 5vw, 2rem);
            }

            :root {
                /* either --dark-mode or --no-dark-mode */
                --color-scheme: var(--dark-mode);

                --font-family: system-ui;

                --fs-300: clamp(0.94rem, calc(0.92rem + 0.08vw), 0.98rem);
                --fs-400: clamp(1.13rem, calc(1.06rem + 0.33vw), 1.31rem);
                --fs-500: clamp(1.35rem, calc(1.21rem + 0.69vw), 1.75rem);
                --fs-600: clamp(1.62rem, calc(1.37rem + 1.24vw), 2.33rem);
                --fs-700: clamp(1.94rem, calc(1.54rem + 2.03vw), 3.11rem);
                --fs-800: clamp(2.33rem, calc(1.7rem + 3.15vw), 4.14rem);
                --fs-900: clamp(2.8rem, calc(1.85rem + 4.74vw), 5.52rem);

                --clr-primary-300: hsl(219, 76%, 55%);
                --clr-primary-400: hsl(219, 76%, 40%);
                --clr-primary-500: hsl(219, 76%, 25%);
                --clr-secondary-300: hsl(269, 75%, 55%);
                --clr-secondary-400: hsl(269, 75%, 40%);
                --clr-secondary-500: hsl(269, 75%, 25%);
                --clr-accent-300: hsl(358, 72%, 65%);
                --clr-accent-400: hsl(358, 72%, 50%);
                --clr-accent-500: hsl(358, 72%, 35%);

                /* settings */
                --no-dark-mode: light;
                --dark-mode: dark light;
            }

            *,
            *::before,
            *::after {
                box-sizing: border-box;
            }

            body {
                margin: 0;
                font-family: var(--font-family);
                font-size: var(--fs-400);
                line-height: 1.6;
            }

            .wrapper {
                width: min(65rem, 100% - 2rem);
                margin-inline: auto;
            }

            .site-title {
                font-size: var(--fs-900);
                line-height: 1.05;
                text-transform: uppercase;
            }

            .section-title {
                font-size: var(--fs-800);
                line-height: 1.1;
            }

            .visually-hidden {
                clip: rect(0 0 0 0);
                clip-path: inset(50%);
                height: 1px;
                overflow: hidden;
                position: absolute;
                white-space: nowrap;
                width: 1px;
            }
        &lt;/style&gt;
    &lt;/head&gt;
    &lt;body&gt;
        &lt;header class="primary-header"&gt;
            &lt;div class="wrapper"&gt;
                &lt;div class="primary-header__inner"&gt;
                    &lt;span class="logo"&gt;LOGO&lt;/span&gt;
                    &lt;ul class="nav-list"&gt;
                        &lt;li&gt;&lt;a href="#"&gt;Home&lt;/a&gt;&lt;/li&gt;
                        &lt;li&gt;&lt;a href="#"&gt;Blog&lt;/a&gt;&lt;/li&gt;
                        &lt;li&gt;&lt;a href="#"&gt;About&lt;/a&gt;&lt;/li&gt;
                        &lt;li&gt;&lt;a href="#"&gt;Contact&lt;/a&gt;&lt;/li&gt;
                    &lt;/ul&gt;
                &lt;/div&gt;
            &lt;/div&gt;
        &lt;/header&gt;

        &lt;main&gt;
            &lt;div class="wrapper"&gt;
                &lt;h1&gt;Lorem ipsum dolor sit amet consectetuer adipiscing elit&lt;/h1&gt;
                &lt;p&gt;
                    Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa &lt;strong&gt;strong&lt;/strong&gt;. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem. Nulla consequat massa quis enim. Donec pede justo, fringilla vel, aliquet nec, vulputate eget, arcu. In enim justo, rhoncus ut, imperdiet a, venenatis vitae, justo. Nullam dictum felis eu pede &lt;a class="external ext" href="#"&gt;link&lt;/a&gt;
                    mollis pretium. Integer tincidunt. Cras dapibus. Vivamus elementum semper nisi. Aenean vulputate eleifend tellus. Aenean leo ligula, porttitor eu, consequat vitae, eleifend ac, enim. Aliquam lorem ante, dapibus in, viverra quis, feugiat a, tellus. Phasellus viverra nulla ut metus varius laoreet. Quisque rutrum. Aenean imperdiet. Etiam ultricies nisi vel augue. Curabitur ullamcorper ultricies nisi.
                &lt;/p&gt;
                &lt;h1&gt;Lorem ipsum dolor sit amet consectetuer adipiscing elit&lt;/h1&gt;
                &lt;h2&gt;Aenean commodo ligula eget dolor aenean massa&lt;/h2&gt;
                &lt;img
                    src="/image-2.jpg"
                    alt="consectetuer adipiscing
          elit"
                /&gt;
                &lt;p&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem.&lt;/p&gt;
                &lt;h2&gt;Aenean commodo ligula eget dolor aenean massa&lt;/h2&gt;
                &lt;p&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem.&lt;/p&gt;
                &lt;ul&gt;
                    &lt;li&gt;Lorem ipsum dolor sit amet consectetuer.&lt;/li&gt;
                    &lt;li&gt;Aenean commodo ligula eget dolor.&lt;/li&gt;
                    &lt;li&gt;Aenean massa cum sociis natoque penatibus.&lt;/li&gt;
                &lt;/ul&gt;
                &lt;p&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem.&lt;/p&gt;
                &lt;form action="#" method="post"&gt;
                    &lt;fieldset&gt;
                        &lt;label for="name"&gt;Name:&lt;/label&gt;
                        &lt;input
                            type="text"
                            id="name"
                            placeholder="Enter your
          full name"
                        /&gt;
                        &lt;label for="email"&gt;Email:&lt;/label&gt;
                        &lt;input
                            type="email"
                            id="email"
                            placeholder="Enter
          your email address"
                        /&gt;
                        &lt;label for="message"&gt;Message:&lt;/label&gt;
                        &lt;textarea
                            id="message"
                            placeholder="What's on your
          mind?"
                        &gt;&lt;/textarea&gt;
                        &lt;input type="submit" value="Send message" /&gt;
                    &lt;/fieldset&gt;
                &lt;/form&gt;
                &lt;img
                    src="/image-3.jpg"
                    alt="consectetuer adipiscing
          elit"
                /&gt;
                &lt;p&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem.&lt;/p&gt;
                &lt;table class="data"&gt;
                    &lt;tr&gt;
                        &lt;th&gt;Entry Header 1&lt;/th&gt;
                        &lt;th&gt;Entry Header 2&lt;/th&gt;
                        &lt;th&gt;Entry Header 3&lt;/th&gt;
                        &lt;th&gt;Entry Header 4&lt;/th&gt;
                    &lt;/tr&gt;
                    &lt;tr&gt;
                        &lt;td&gt;Entry First Line 1&lt;/td&gt;
                        &lt;td&gt;Entry First Line 2&lt;/td&gt;
                        &lt;td&gt;Entry First Line 3&lt;/td&gt;
                        &lt;td&gt;Entry First Line 4&lt;/td&gt;
                    &lt;/tr&gt;
                    &lt;tr&gt;
                        &lt;td&gt;Entry Line 1&lt;/td&gt;
                        &lt;td&gt;Entry Line 2&lt;/td&gt;
                        &lt;td&gt;Entry Line 3&lt;/td&gt;
                        &lt;td&gt;Entry Line 4&lt;/td&gt;
                    &lt;/tr&gt;
                    &lt;tr&gt;
                        &lt;td&gt;Entry Last Line 1&lt;/td&gt;
                        &lt;td&gt;Entry Last Line 2&lt;/td&gt;
                        &lt;td&gt;Entry Last Line 3&lt;/td&gt;
                        &lt;td&gt;Entry Last Line 4&lt;/td&gt;
                    &lt;/tr&gt;
                &lt;/table&gt;
                &lt;p&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem.&lt;/p&gt;
            &lt;/div&gt;
        &lt;/main&gt;

        &lt;script&gt;
            // For this tutorial on YT:
            // https://youtu.be/V-CBdlfCPic

            const primaryHeader = document.querySelector('.primary-header');
            const scrollWatcher = document.createElement('div');

            scrollWatcher.setAttribute('data-scroll-watcher', '');
            primaryHeader.before(scrollWatcher);

            const navObserver = new IntersectionObserver(
                entries =&gt; {
                    primaryHeader.classList.toggle('sticking', !entries[0].isIntersecting);
                },
                { rootMargin: '500px 0px 0px 0px' }
            );

            navObserver.observe(scrollWatcher);
        &lt;/script&gt;
    &lt;/body&gt;
&lt;/html&gt;
</pre>