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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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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

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import usage.

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HTML
!

CSS 

              
                body
	background: #222

canvas
	position: absolute
	top: 50%
	left: 50%
	transform: translate3d(-50%, -50%, 0)
	box-shadow: 0 0 24px 8px rgba(0, 0, 0, 0.2)
!

JS 

              
                const L = 600;
const N = 50;
const COLOR = [180, 50, 120];
const SPEED = 1 / 8;
const R_MAX = L * 3;

const PI2 = Math.PI * 2;
const canvas = document.createElement('canvas');
canvas.height = canvas.width = L;
canvas.style.height = canvas.style.width = `${L / 2}px`;
document.body.appendChild(canvas);

const ctx = canvas.getContext('2d');
ctx.lineWidth = 2;
ctx.strokeStyle = `rgb(${COLOR})`;
ctx.globalCompositeOperation = 'lighter';

// Cache the x and y values for fast lookup.
const xBuffer = new ArrayBuffer(N * Uint16Array.BYTES_PER_ELEMENT);
const yBuffer = new ArrayBuffer(N * Uint16Array.BYTES_PER_ELEMENT);
const x = new Int16Array(xBuffer);
const y = new Int16Array(yBuffer);
for (let n = 0; n < N; n++) {
	const angle = n * PI2 / N;
	x[n] = (1.5 + Math.cos(angle)) * L / 3;
	y[n] = (1.5 + Math.sin(angle)) * L / 3;
}

(function draw (t) {
	ctx.clearRect(0, 0, L, L);
	for (let n = 0; n < N; n++) {
		const R = (t * SPEED + n / N * R_MAX) % R_MAX;
		ctx.beginPath();
		ctx.fillStyle = `rgba(${COLOR}, ${R_MAX / N / R})`;
		ctx.arc(x[n], y[n], R, 0, PI2);
		ctx.stroke();
		ctx.fill();
	}
	
	requestAnimationFrame(draw);
})(0);
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999px

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