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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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About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient. For instance, CoffeeScript can help prevent easy-to-make mistakes and offer a cleaner syntax and Babel can bring ECMAScript 6 features to browsers that only support ECMAScript 5.

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HTML

            
              .wrapper-box.u-centercontent
	.aspectratio(data-ratio="16:9")
		div.u-centercontent
			p.u-centertext This text should appear in a green box which has a 16:9 aspect-ratio.<br />The green box itself is contained in a blue box of at least 500px in height.
!

CSS

            
              /*

There's a bug in Firefox where percentage based padding is not calculated correctly for an element wrapped inside a flexboxed element.

Normally percentage based padding is calculated with respect to the width of said element.

In Firefox however, the height of .aspectratio is always 281.25px, which happens to be 56.25% of the *height* of its parent element.

Try toggling the "display: flex" line (used to center the content vertically), and resize your browser window. You'll see.

Related Blog Post: https://www.bram.us/2017/07/30/vertical-marginspaddings-and-flexbox-a-quirky-combination/

Firefox Bug Report: https://bugzilla.mozilla.org/show_bug.cgi?id=1315669

*/

body
	background white
 	width 100%
	height 100%
	
// Utility class to center content using flexbox
.u-centercontent
	display flex
	align-items center
	justify-content center
	
// Utiltity class to center text
.u-centertext
	text-align center

// The wrapper box
.wrapper-box
	width 100%
	height 500px
	
	// For demo purposes, color me blue
	background blue
	
	> .aspectratio

		// For demo purposes, color my contained ar box green
		background lime
	
// CSS to create boxes with fixed aspect ratios.
// See https://www.bram.us/2017/06/16/aspect-ratios-in-css-are-a-hack/ for more info
.aspectratio
	width 100%
	height 0
	position relative
	
	&[data-ratio="16:9"]
		padding-top: 56.25%;
	
	&[data-ratio="4:3"]
		padding-top: 75%;
		
	> *
		position absolute
		top 0
		left 0
		width 100%
		height 100%
!

JS
!
999px
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