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HTML 

              
                <main>
	<h1>❤️ CSS Grid Slider w/ Variables</h1>

	<p>With the magic of <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_Layout" target="_blank" rel="noopener">CSS Grid</a>, <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Scroll_Snap/Basic_concepts" target="_blank" rel="noopener">CSS Scroll Snap</a>, and <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_custom_properties" target="_blank" rel="noopener">CSS Variables</a> (plus a dash of <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/:where" target="_blank" rel="noopener"><code>:where()</code> for specificity)</a>, you can make a dead-simple, ultra-lightweight, fully-customizable CSS slider with just a few lines of code.</p>
	<p>✏️ Try making edits in the <strong>CSS panel</strong> to see how it works.</p>
	
	<ul class="slider colors">
		<li>Slide #1</li>
		<li>Slide #2</li>
		<li>Slide #3</li>
		<li>Slide #4</li>
		<li>Slide #5</li>
		<li>Slide #6</li>
		<li>Slide #7</li>
	</ul>
	
	<p>You can adjust <code>--slider-visible-slides</code> to change the number of slides visible at one time. (Fun&nbsp;Fact: Floating point values work too! The slider after this only shows 1⅔ slides at a time…)</em></p>
	<ul class="slider slider--cool">
		<li>Slide #1</li>
		<li>Slide #2</li>
		<li>Slide #3</li>
		<li>Slide #4</li>
		<li>Slide #5</li>
		<li>Slide #6</li>
		<li>Slide #7</li>
	</ul>

	<p>You can also use <code>--slider-gutter</code> to adjust the gutter (spacing) between each slide—or you could set it to 0 to remove the space if you want. It all works!</p>
	<ul class="slider slider--gray">
		<li>Slide #1</li>
		<li>Slide #2</li>
		<li>Slide #3</li>
		<li class="js-scroll-to-center">Slide #4</li>
		<li>Slide #5</li>
		<li>Slide #6</li>
		<li>Slide #7</li>
	</ul>

	<p>Oh yeah, and did I mention with a little JavaScript (<a href="https://developer.mozilla.org/en-US/docs/Web/API/Element/scroll" target="_blank" rel="noopener"><code>Element.scroll()</code></a>) you can have your sliders centered on an active slide immediately on page load. How cool is that?!</p>
	<p>👌 It’s amazing what you can do these days.</p>

	<h2>Code</h2>
	<h3>CSS</h3>
<pre><code>:where(.slider) {
	/* Change these to adjust your slider. */
	--slider-visible-slides: 3;
	--slider-gutter: 10px;
	--slider-scrollbar-size: 15px;

	/* Math... */
	--slider-slide-width: calc((100% - (var(--slider-visible-slides) - 1) * var(--slider-gutter)) / var(--slider-visible-slides));

	/* Put it all together! */
	display: grid;
	grid: 1fr / auto-flow var(--slider-slide-width);
	grid-gap: var(--slider-gutter);
	margin: 0;
	padding: 0 0 var(--slider-scrollbar-size);
	overflow: scroll;
	list-style: none;
	scroll-snap-type: x mandatory;
	overscroll-behavior: contain;
}

:where(.slider > *) {
	margin: 0;
	padding: 0;
	scroll-snap-align: start;
}</code></pre>
	<h3>JavaScript</h3>
<pre><code>[...document.querySelectorAll('.js-scroll-to-center')].forEach((el) => {
	el.parentNode.scroll({ left: el.offsetLeft - el.parentNode.offsetWidth / 2 + el.offsetWidth / 2 });
});</code></pre>
	
	<h2>References</h2>
	<ul>
		<li>🙌 <a href="https://twitter.com/_ynotdraw/status/1424779601805553667" target="_blank" rel="noopener">Tony Ward’s tweet about these styles for his image uploader</a></li>
		<li>🙏 <a href="https://twitter.com/argyleink" target="_blank" rel="noopener">Adam Argyle’s constant CSS inspiration</a></li>
		<li><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_Layout" target="_blank" rel="noopener">MDN: CSS Grid Layout</a></li>
		<li><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Scroll_Snap/Basic_concepts" target="_blank" rel="noopener">MDN: Basic concepts of CSS Scroll Snap</a></li>
		<li><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_custom_properties" target="_blank" rel="noopener">MDN: Using CSS custom properties (variables)</a></li>
		<li><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/:where" target="_blank" rel="noopener">MDN: :where()</a></li>
		<li><a href="https://developer.mozilla.org/en-US/docs/Web/API/Element/scroll" target="_blank" rel="noopener">MDN: Element.scroll()</a></li>
	</ul>
</main>
!

CSS 

              
                
/**
 * CSS Grid Slider.
 * ------------------------------
 * Use :where() to reduce specificity, so
 * other classes can override these styles.
 */
:where(.slider) {
	/* Change these to adjust your slider. */
	--slider-visible-slides: 3;
	--slider-gap: 10px;
	--slider-scrollbar-size: 15px;

	/* Math... */
	--slider-slide-width: calc((100% - (var(--slider-visible-slides) - 1) * var(--slider-gap)) / var(--slider-visible-slides));

	/* Put it all together! */
	display: grid;
	position: relative;
	grid-auto-columns: var(--slider-slide-width);
	grid-auto-flow: column;
	gap: var(--slider-gap);
	margin: 0;
	padding: 0 0 var(--slider-scrollbar-size);
	overflow: auto;
	list-style: none;
	scroll-snap-type: x mandatory;
	overscroll-behavior-x: contain;
}

:where(.slider > *) {
	margin: 0;
	padding: 0;
	scroll-snap-align: start;
}



/* ------------------------------ */
/* Demo Styles                    */
/* ------------------------------ */

.slider li {
	padding: 1rem;
	border: 2px solid black;
}

.slider--cool {
	--slider-visible-slides: 2;
	margin-block: 1rem;
}

.slider--cool li {
	border-radius: 5px;
	border-color: lightblue;
	background: blue;
	color: white;
}

.slider--gray {
	--slider-visible-slides: 1.667;
	--slider-gap: 30px;
	margin-block: 1rem;
	text-align: center;
}

.slider--gray li {
	border: 0;
	background: lightgray;
	scroll-snap-align: center;
}



/* ------------------------------ */
/* Reset Styles                   */
/* ------------------------------ */

html {
	box-sizing: border-box;
}

*,
::after,
::before {
	box-sizing: inherit;
}

body {
	margin: 1rem auto 3rem;
	line-height: 1.4;
	tab-size: 4;
}

main {
	display: block;
	max-width: 42rem;
	margin: 0 auto;
	padding-right: 1rem;
	padding-left: 1rem;
}

h2 {
	 margin-top: 3rem;
}

pre {
	padding: 1rem;
	overflow: auto;
	border: 1px solid #ccc;
	-webkit-overflow-scroll: touch;
}

.colors > *:nth-child(7n + 1) { background-color: red; }
.colors > *:nth-child(7n + 2) { background-color: orange; }
.colors > *:nth-child(7n + 3) { background-color: yellow; }
.colors > *:nth-child(7n + 4) { background-color: green; }
.colors > *:nth-child(7n + 5) { background-color: blue; }
.colors > *:nth-child(7n + 6) { background-color: indigo; }
.colors > *:nth-child(7n + 7) { background-color: violet; }
!

JS 

              
                /**
 * Center active slides on page load.
 */
[...document.querySelectorAll('.js-scroll-to-center')].forEach((el) => {
	el.parentNode.scroll({ left: el.offsetLeft - el.parentNode.offsetWidth / 2 + el.offsetWidth / 2 });
});
!
999px

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