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HTML

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About the <head>

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <script src="https://rawcdn.githack.com/flackr/scroll-timeline/c7a034a3d8fdecbd13bf3939ee5d6f6293bd6952/dist/scroll-timeline.js"></script>
<div id="progress"></div>
<main>
	<h1>The Polar Bear</h1>
	
	<div class="warning">
		<p>⚠️ Your browser does not support Scroll-Linked Animations with CSS <code>scroll-timeline: scroll()</code>. Please try Chrome 107+ with the “Experimental Web Platform Features” flag enabled.</p>
		<p>To make this demo work in your browser, <a href="https://github.com/flackr/scroll-timeline">a polyfill</a> has been loaded.</p>
	</div>

	<div class="warning warning--info">
		<p>ℹ️ Alternatively, <a href="https://codepen.io/bramus/pen/RwMZQJV" target="_top">check out a WAAPI powered version</a>.</p>
	</div>
	
	<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer mattis turpis eu neque tincidunt lacinia. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Aliquam auctor ultrices tortor et volutpat. Donec eu semper orci, eu fermentum orci. Vivamus aliquam lobortis egestas. Proin vel mauris vitae sem auctor cursus. Aenean sit amet odio at magna pharetra luctus nec eget urna. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia curae; Praesent in leo at tellus ultricies laoreet.</p>

	<p>Nam pulvinar congue condimentum. Pellentesque fringilla ante sed massa tincidunt feugiat. Nulla bibendum est eros, non malesuada dolor vehicula in. Morbi eu cursus arcu. Phasellus ultricies ornare lorem, non interdum orci condimentum eu. Donec condimentum condimentum ligula ut placerat. Vestibulum id neque condimentum, molestie nunc vel, suscipit turpis. Quisque orci velit, mattis et nibh non, tempor finibus erat. Nullam tristique, tortor non commodo cursus, magna turpis rhoncus leo, quis porta quam ante sed orci. Nunc vehicula imperdiet leo in vulputate. Quisque quis dolor orci.</p>

	<p>Curabitur ultrices fringilla libero sit amet porta. Nulla rhoncus venenatis euismod. Praesent non interdum sem. Nunc in nibh tincidunt, faucibus sem at, finibus turpis. Nullam vel odio blandit, tincidunt urna et, luctus lectus. Vivamus porta sem vitae turpis interdum porta eu id ligula. Fusce non nisi fringilla, malesuada metus ut, imperdiet ligula. Nunc quis lorem nibh. Duis pharetra magna vestibulum metus convallis, id mollis ligula vulputate. Sed purus est, consectetur non suscipit sit amet, hendrerit at dolor. Maecenas feugiat, quam vel ullamcorper feugiat, sapien ipsum viverra justo, id cursus metus nisi quis enim.</p>

	<p>Duis nec nisi a eros dictum euismod nec non enim. Donec augue neque, aliquam id finibus a, volutpat ut ligula. Nam feugiat odio elit, ut molestie mi tempus vel. Etiam vitae velit eget massa scelerisque hendrerit cursus vel justo. Sed eget euismod lectus. Morbi tincidunt diam ac diam tempor molestie. Mauris eget lectus leo. Etiam id porta turpis.</p>

	<p>Aenean ac pellentesque ante. In hac habitasse platea dictumst. Nullam efficitur, dolor ac pharetra iaculis, sem elit maximus ex, et malesuada est ipsum tempor nisi. Phasellus auctor et turpis ultrices fermentum. Mauris ac orci sapien. Quisque auctor, mi eu vestibulum dictum, nisl felis pulvinar dui, non dictum justo tellus a urna. Morbi suscipit et odio a feugiat. Sed dui nisi, iaculis a lacus posuere, dictum laoreet felis. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.</p>

	<p><img src="https://assets.codepen.io/89905/photo-1610570426407-efa770f9d31a.jpeg?width=1635&height=1090&format=auto&quality=60" alt="" title="" width="1080" height="720" class="revealing-image" id="revealing-image-1" /><br /><a href="https://unsplash.com/photos/PX_1j-M59I8">Polar bear walking</a> by <a href="https://unsplash.com/@dtbosse">Daniel Bosse</a></p>

	<p>Nam pulvinar congue condimentum. Pellentesque fringilla ante sed massa tincidunt feugiat. Nulla bibendum est eros, non malesuada dolor vehicula in. Morbi eu cursus arcu. Phasellus ultricies ornare lorem, non interdum orci condimentum eu. Donec condimentum condimentum ligula ut placerat. Vestibulum id neque condimentum, molestie nunc vel, suscipit turpis. Quisque orci velit, mattis et nibh non, tempor finibus erat. Nullam tristique, tortor non commodo cursus, magna turpis rhoncus leo, quis porta quam ante sed orci. Nunc vehicula imperdiet leo in vulputate. Quisque quis dolor orci.</p>

	<p>Curabitur ultrices fringilla libero sit amet porta. Nulla rhoncus venenatis euismod. Praesent non interdum sem. Nunc in nibh tincidunt, faucibus sem at, finibus turpis. Nullam vel odio blandit, tincidunt urna et, luctus lectus. Vivamus porta sem vitae turpis interdum porta eu id ligula. Fusce non nisi fringilla, malesuada metus ut, imperdiet ligula. Nunc quis lorem nibh. Duis pharetra magna vestibulum metus convallis, id mollis ligula vulputate. Sed purus est, consectetur non suscipit sit amet, hendrerit at dolor. Maecenas feugiat, quam vel ullamcorper feugiat, sapien ipsum viverra justo, id cursus metus nisi quis enim.</p>

	<p>Duis nec nisi a eros dictum euismod nec non enim. Donec augue neque, aliquam id finibus a, volutpat ut ligula. Nam feugiat odio elit, ut molestie mi tempus vel. Etiam vitae velit eget massa scelerisque hendrerit cursus vel justo. Sed eget euismod lectus. Morbi tincidunt diam ac diam tempor molestie. Mauris eget lectus leo. Etiam id porta turpis.</p>

	<p>Aenean ac pellentesque ante. In hac habitasse platea dictumst. Nullam efficitur, dolor ac pharetra iaculis, sem elit maximus ex, et malesuada est ipsum tempor nisi. Phasellus auctor et turpis ultrices fermentum. Mauris ac orci sapien. Quisque auctor, mi eu vestibulum dictum, nisl felis pulvinar dui, non dictum justo tellus a urna. Morbi suscipit et odio a feugiat. Sed dui nisi, iaculis a lacus posuere, dictum laoreet felis. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.</p>

	<p><img src="https://assets.codepen.io/89905/photo-1610570311113-79ba0e69768d.jpeg?width=1635&height=1090&format=auto&quality=60" alt="" title="" width="1080" height="720" class="revealing-image" id="revealing-image-2" /><br /><a href="https://unsplash.com/photos/Fk4Y_VkUlSQ">Polar bear shaking off water</a> by <a href="https://unsplash.com/@dtbosse">Daniel Bosse</a></p>

	<p>Curabitur ultrices fringilla libero sit amet porta. Nulla rhoncus venenatis euismod. Praesent non interdum sem. Nunc in nibh tincidunt, faucibus sem at, finibus turpis. Nullam vel odio blandit, tincidunt urna et, luctus lectus. Vivamus porta sem vitae turpis interdum porta eu id ligula. Fusce non nisi fringilla, malesuada metus ut, imperdiet ligula. Nunc quis lorem nibh. Duis pharetra magna vestibulum metus convallis, id mollis ligula vulputate. Sed purus est, consectetur non suscipit sit amet, hendrerit at dolor. Maecenas feugiat, quam vel ullamcorper feugiat, sapien ipsum viverra justo, id cursus metus nisi quis enim.</p>
	<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer mattis turpis eu neque tincidunt lacinia. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Aliquam auctor ultrices tortor et volutpat. Donec eu semper orci, eu fermentum orci. Vivamus aliquam lobortis egestas. Proin vel mauris vitae sem auctor cursus. Aenean sit amet odio at magna pharetra luctus nec eget urna. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia curae; Praesent in leo at tellus ultricies laoreet.</p>

	<p>Duis nec nisi a eros dictum euismod nec non enim. Donec augue neque, aliquam id finibus a, volutpat ut ligula. Nam feugiat odio elit, ut molestie mi tempus vel. Etiam vitae velit eget massa scelerisque hendrerit cursus vel justo. Sed eget euismod lectus. Morbi tincidunt diam ac diam tempor molestie. Mauris eget lectus leo. Etiam id porta turpis.</p>

	<p>Aenean ac pellentesque ante. In hac habitasse platea dictumst. Nullam efficitur, dolor ac pharetra iaculis, sem elit maximus ex, et malesuada est ipsum tempor nisi. Phasellus auctor et turpis ultrices fermentum. Mauris ac orci sapien. Quisque auctor, mi eu vestibulum dictum, nisl felis pulvinar dui, non dictum justo tellus a urna. Morbi suscipit et odio a feugiat. Sed dui nisi, iaculis a lacus posuere, dictum laoreet felis. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.</p>

	<p>Curabitur ultrices fringilla libero sit amet porta. Nulla rhoncus venenatis euismod. Praesent non interdum sem. Nunc in nibh tincidunt, faucibus sem at, finibus turpis. Nullam vel odio blandit, tincidunt urna et, luctus lectus. Vivamus porta sem vitae turpis interdum porta eu id ligula. Fusce non nisi fringilla, malesuada metus ut, imperdiet ligula. Nunc quis lorem nibh. Duis pharetra magna vestibulum metus convallis, id mollis ligula vulputate. Sed purus est, consectetur non suscipit sit amet, hendrerit at dolor. Maecenas feugiat, quam vel ullamcorper feugiat, sapien ipsum viverra justo, id cursus metus nisi quis enim.</p>
	<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer mattis turpis eu neque tincidunt lacinia. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Aliquam auctor ultrices tortor et volutpat. Donec eu semper orci, eu fermentum orci. Vivamus aliquam lobortis egestas. Proin vel mauris vitae sem auctor cursus. Aenean sit amet odio at magna pharetra luctus nec eget urna. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia curae; Praesent in leo at tellus ultricies laoreet.</p>

	<p>Duis nec nisi a eros dictum euismod nec non enim. Donec augue neque, aliquam id finibus a, volutpat ut ligula. Nam feugiat odio elit, ut molestie mi tempus vel. Etiam vitae velit eget massa scelerisque hendrerit cursus vel justo. Sed eget euismod lectus. Morbi tincidunt diam ac diam tempor molestie. Mauris eget lectus leo. Etiam id porta turpis.</p>

	<p>Aenean ac pellentesque ante. In hac habitasse platea dictumst. Nullam efficitur, dolor ac pharetra iaculis, sem elit maximus ex, et malesuada est ipsum tempor nisi. Phasellus auctor et turpis ultrices fermentum. Mauris ac orci sapien. Quisque auctor, mi eu vestibulum dictum, nisl felis pulvinar dui, non dictum justo tellus a urna. Morbi suscipit et odio a feugiat. Sed dui nisi, iaculis a lacus posuere, dictum laoreet felis. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.</p>
</main>
!

CSS 

              
                @supports (animation-timeline: scroll()) {
	/* Hide warning when native support */
	.warning {
		display: none;
	}
}

/* Scroll-Linked Animation */
@keyframes grow-progress {
	from {
		transform: scaleX(0);
	}
	to {
		transform: scaleX(1);
	}
}

#progress {
	animation: grow-progress auto linear;
	animation-timeline: scroll();
}

#progress {
	position: fixed;
	z-index: 10;
	left: 0;
	top: 0;
	width: 100%;
	height: 1em;
	transform-origin: 0 50%;
	background: red;
}

/** NON ESSENTIAL STYLES BELOW **/
html {
	color-scheme: light dark;
}
html,
body {
	margin: 0;
	padding: 0;
}

body {
	font-size: clamp(1.1em, calc(0.5em + 1vw), 3em);
	line-height: 1.42;
	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
}

main {
	font-weight: 300;
	width: 90vw;
	max-width: 40em;
	margin: 0 auto;
	padding: 4em 0;
}

main img {
	width: 100%;
	height: auto;
}

.warning {
	padding: 1em;
	margin: 1em 0;
	border: 1px solid #ccc;
	background: rgba(255 255 205 / 0.8);
}

.warning > :first-child {
	margin-top: 0;
}

.warning > :last-child {
	margin-bottom: 0;
}

.warning a {
	color: blue;
}
.warning--info {
	border: 1px solid #123456;
	background: rgb(205 230 255 / 0.8);
}
.warning--alarm {
	border: 1px solid red;
	background: #ff000010;
}

@media (prefers-color-scheme: dark) {
	.warning {
		background: #333;
	}
	.warning a {
		color: lightblue;
	}
	.warning--info {
		border-color: lightblue;
	}
}
!

JS 

              
                import { showDialog } from 'https://codepen.io/bramus/pen/ZEqMOLz/cccfe67c2b9cdfbeb5fb59083dbd0a64.js';
showDialog('https://scroll-driven-animations.style/demos/progress-bar/css/');

// Alternative Versions:
// - JS ScrollTimeline 2022 + Polyfill: https://codepen.io/bramus/pen/RwMZQJV
// - CSS scroll-timeline 2022 + Polyfill: https://codepen.io/bramus/pen/KKoGNye 👈 = The version you are currently looking at
// - CSS scroll-timeline 2022 + Polyfill (Extended Syntax 1): https://codepen.io/bramus/pen/gOzwZaN
// - CSS scroll-timeline 2022 + Polyfill (Extended Syntax 2): https://codepen.io/bramus/pen/ExLgGKQ
// - JS Motion One: https://codepen.io/bramus/pen/GRxvOgx
// - (Old) CSS @scroll-timeline 2021 + Polyfill: https://codepen.io/bramus/pen/WNGLpyV
!
999px

Console