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HTML

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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <article>
	<h1>How to create a pop-up without JavaScript</h1>
	<p>Ever wanted a pop-up mechanism on your website, but you don't want to use JavaScript? Here's how:</p>
	<ol>
		<li>Add a <code>&lt;details&gt;</code> and <code>&lt;summary&gt;</code> to your document</li> 
		<li>Insert a <code>&lt;div&gt;</code> to your <code>&lt;details&gt;</code> element</li>
		<li>Add a scaling animation to this <code>&lt;div&gt;</code></li>
		<li>Add this animation to the <code>&lt;div&gt;</code> when the <code>[open]</code> attribute is toggled on the <code>&lt;details&gt;</code> element</li>
	</ol>
	<p>Toggle the <strong>How it works</strong> button for more info.</p>

</article>

<details>
	<summary>How it works<svg xmlns="http://www.w3.org/2000/svg" width="192" height="192" fill="currentColor" viewBox="0 0 256 256"><rect width="256" height="256" fill="none"></rect><circle cx="128" cy="128" r="96" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"></circle><circle cx="128" cy="180" r="12"></circle><path d="M127.9995,144.0045v-8a28,28,0,1,0-28-28" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"></path></svg></summary>
	<div>
			<p>The scaling effect you see when you open this <code>&lt;details&gt;</code> element is created by using a keyframe animation.</p>
		<p><pre><code>@keyframes scale { 
&nbsp;0% {
&nbsp;&nbsp;transform: scale(0);
&nbsp;}
&nbsp;100% {
&nbsp;&nbsp;transform: scale(1);
&nbsp;}
}</code></pre> </p>
<p>This animation is added to the <code>&lt;div&gt;</code>, but only when the <code>[open]</code> attribute is toggled.</p>
<p><pre><code>details[open] div { 
&nbsp;animation: scale .15s ease;
}</code></pre></p>
	<p>Sadly there's no way (that I know of) to animate the  <code>&lt;div&gt;</code> when the  <code>&lt;details&gt;</code> is closing.</p>
	</div>
</details>
!

CSS 

              
                @import url("https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&display=swap");

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

body {
	font-family: "Inter", sans-serif;
	line-height: 1.5;
	min-height: 100vh;
	background-color: #f4f5f7;
	padding-top: 10vh;
	padding-bottom: 10vh;
}

strong {
	font-weight: 600;
}

article {
	width: 90%;
	max-width: 600px;
	margin-left: auto;
	margin-right: auto;
	font-size: 1.125rem;
	padding: 2rem;
	background-color: #fff;
	border-radius: 10px;
	box-shadow: 0 15px 20px -10px rgba(#000, 0.1);

	& > * + * {
		margin-top: 1em;
	}

	&:is(h1, h2, h3) + * {
		margin-top: 0.5em;
	}

	h1 {
		font-weight: 900;
		font-size: 2rem;
		line-height: 1.125;
	}

	code {
		background-color: #eee;
		font-weight: 600;
		font-family: monospace;
	}

	p {
	}

	ol {
		counter-reset: sickstuff;
		li {
			position: relative;
			padding-left: 32px;
			counter-increment: sickstuff;
			& + li {
				margin-top: 0.5em;
			}
			&:before {
				content: counter(sickstuff);
				width: 24px;
				height: 24px;
				position: absolute;
				left: 0;
				top: calc((1.125rem * 1.5) - 24px);
				font-size: 0.75em;
				border-radius: 50%;
				display: inline-flex;
				align-items: center;
				justify-content: center;
				background-color: #185adb;
				color: #fff;
				font-weight: 600;
			}
		}
	}
}

details {
	position: fixed;
	right: 1rem;
	bottom: 1rem;
	margin-top: 2rem;
	color: #6b7280;
	display: flex;
	flex-direction: column;

	div {
		background-color: #1e1e27;
		box-shadow: 0 5px 10px rgba(#000, 0.15);
		padding: 1.25rem;
		border-radius: 8px;
		position: absolute;
		max-height: calc(100vh - 100px);
		width: 400px;
		max-width: calc(100vw - 2rem);
		bottom: calc(100% + 1rem);
		right: 0;
		overflow: auto;
		transform-origin: 100% 100%;
		color: #95a3b9;
		&::-webkit-scrollbar {
			width: 15px;
			background-color:#1e1e27;
		}

		&::-webkit-scrollbar-thumb {
			width: 5px;
			border-radius: 99em;
			background-color: #95a3b9;
			border: 5px solid #1e1e27;
		}
		& > * + * {
			margin-top: 0.75em;
		}

		p > code {
			font-size: 1rem;
			font-family: monospace;
		}

		pre {
			white-space: pre-line;
			// background-color: #2c2d38;
			border: 1px solid #95a3b9;
			border-radius: 6px;
			font-family: monospace;
			padding: 0.75em;
			font-size: 0.875rem;
			color: #fff;
		}
	}

	&[open] div {
		animation: scale 0.25s ease;
	}
}

summary {
	display: inline-flex;
	margin-left: auto;
	margin-right: auto;
	justify-content: center;
	align-items: center;
	font-weight: 600;
	padding: 0.75em 3em .75em 1.25em;
	border-radius: 99em;
	color: #fff;
	background-color: #185adb;
	box-shadow: 0 5px 15px rgba(#000, 0.1);
	list-style: none;
	text-align: center;
	cursor: pointer;
	transition: 0.15s ease;
	position: relative;
	&::-webkit-details-marker {
		display: none;
	}

	&:hover,
	&:focus {
		background-color: mix(#000, #185adb, 20%);
		// color: #6366f1;
	}

	svg {
		position: absolute;
		right: 1.25em;
		top: 50%; 
		transform: translateY(-50%);
		width: 1.5em;
		height: 1.5em;
	}
}

@keyframes scale {
	0% {
		transform: scale(0);
	}
	100% {
		transform: scale(1);
	}
}
!

JS 

              
                // Nope
!
999px

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